Reference Guide: What does this symbol mean in PHP? (PHP Syntax)

Question

What is this?

This is a collection of questions that come up now and then about syntax in PHP. This is also a Community Wiki, so everyone is invited to participate in maintaining this list.

This question shouldn't be used as a dupe target for closing questions. Use actual questions linked here as dupe targets instead.

Why is this?

It used to be hard to find questions about operators and other syntax tokens.¹
The main idea is to have links to existing questions on Stack Overflow, so it's easier for us to reference them, and not to copy over content from the PHP Manual.

Note: Since January 2013, Stack Overflow does support special characters. Just surround the search terms by quotes, e.g. [php] "==" vs "==="

What should I do here?

If you have been pointed here by someone because you have asked such a question, please find the particular syntax below. The linked pages to the PHP manual along with the linked questions will likely answer your question then. If so, you are encouraged to upvote the answer. This list is not meant as a substitute for the help others provide.

The List

If your particular token is not listed below, you might find it in the List of Parser Tokens.

& Bitwise Operators or References

=& References

&= Bitwise Operators

&& Logical Operators

% Arithmetic Operators

!! Logical Operators

Double not (!!) operator in PHP

@ Error Control Operators

?: Ternary Operator

Double question mark

?? Null Coalesce Operator (since PHP 7)

C#'s null coalescing operator (??) in PHP

A question mark followed by a type declaration

?string ?int ?array ?bool ?float Nullable type declaration (since PHP 7.1)

?-> question mark followed by object operator is a NullSafe Operator (since PHP 8.0)

Is there a "nullsafe operator" in PHP?

: Alternative syntax for control structures, Ternary Operator, Return Type Declaration

:: Scope Resolution Operator

\ Namespaces

-> Classes And Objects

=> Arrays

^ Bitwise Operators

>> Bitwise Operators

What does >> mean in PHP?

<< Bitwise Operators

Strange print behaviour in PHP?

<<< Heredoc or Nowdoc

= Assignment Operators

The 3 different equals

== Comparison Operators

=== Comparison Operators

!== Comparison Operators

!= Comparison Operators

<> Comparison Operators

<=> Comparison Operators (since PHP 7.0)

Spaceship (three way comparison) operator

| Bitwise Operators

|| Logical Operators

~ Bitwise Operators

What does this ~ operator mean here?

+ Arithmetic Operators, Array Operators

Merging two arrays with the "+" (array union operator) How does it work?

+= and -= Assignment Operators

++ and -- Incrementing/Decrementing Operators

.= Assignment Operators

. String Operators

, Function Arguments

Difference between period and comma when concatenating with echo versus return?

, Variable Declarations

What do commas mean in a variable declaration?

$$ Variable Variables

` Execution Operator

What are the backticks `` called?

<?= Short Open Tags

[] Arrays (short syntax since PHP 5.4)

<? Opening and Closing tags

Are PHP short tags acceptable to use?

.. Double-dot character range

Native PHP functions that allow double-dot range syntax

... Argument unpacking (since PHP 5.6)

** Exponentiation (since PHP 5.6)

# One-line shell-style comment

Can I use hashes for comments in PHP?

#[] Attributes (since PHP 8)

I know this isn't strictly PHP, but what about including a link to phpdoc.org for phpDocumentor comment syntax, which is commonly used and it's also impossible to search for /**? — Mike, Commented Aug 21, 2011 at 2:25
I ran into this problem a lot too (not being able to search for special characters), which is why I made SymbolHound, a search engine that doesn't ignore special characters. I also posted it on StackApps. — dncrane, Commented Dec 6, 2011 at 18:34
@davejal: Please make sure a tag applies instead of simply blindly adding it. — Deduplicator, Commented Jan 15, 2016 at 23:19
Here's the names of all the PHP operators (TOKEN). Reference php.net/manual/en/tokens.php ![enter image description here](i.sstatic.net/P5ilY.jpg) — Mahmoud Zalt, Commented Nov 23, 2017 at 0:04

16 revs, 9 users 80% · Accepted Answer · 2018-11-12 08:39:50Z

Incrementing / Decrementing Operators

++ increment operator

-- decrement operator

Example    Name              Effect
---------------------------------------------------------------------
++$a       Pre-increment     Increments $a by one, then returns $a.
$a++       Post-increment    Returns $a, then increments $a by one.
--$a       Pre-decrement     Decrements $a by one, then returns $a.
$a--       Post-decrement    Returns $a, then decrements $a by one.

These can go before or after the variable.

If put before the variable, the increment/decrement operation is done to the variable first then the result is returned. If put after the variable, the variable is first returned, then the increment/decrement operation is done.

For example:

$apples = 10;
for ($i = 0; $i < 10; ++$i) {
    echo 'I have ' . $apples-- . " apples. I just ate one.\n";
}

Live example

In the case above ++$i is used, since it is faster. $i++ would have the same results.

Pre-increment is a little bit faster because it really increments the variable and after that 'returns' the result. Post-increment creates a special variable, copies there the value of the first variable and only after the first variable is used, replaces its value with second's.

However, you must use $apples--, since first, you want to display the current number of apples, and then you want to subtract one from it.

You can also increment letters in PHP:

$i = "a";
while ($i < "c") {
    echo $i++;
}

Once z is reached aa is next, and so on.

Note that character variables can be incremented but not decremented and even so only plain ASCII characters (a-z and A-Z) are supported.

Stack Overflow Posts:

Understanding Incrementing

3 revs, 3 users 62% · Accepted Answer · 2016-09-19 12:15:00Z

Bitwise Operator

What is a bit? A bit is a representation of 1 or 0. Basically OFF(0) and ON(1)

What is a byte? A byte is made up of 8 bits and the highest value of a byte is 255, which would mean every bit is set. We will look at why a byte's maximum value is 255.

-------------------------------------------
|      1 Byte ( 8 bits )                  |
-------------------------------------------
|Place Value | 128| 64| 32| 16| 8| 4| 2| 1|     
-------------------------------------------

This representation of 1 Byte

1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255 (1 Byte)

A few examples for better understanding

The "AND" operator: `&`

$a =  9;
$b = 10;
echo $a & $b;

This would output the number 8. Why? Well let's see using our table example.

-------------------------------------------
|      1 Byte ( 8 bits )                  |
-------------------------------------------
|Place Value | 128| 64| 32| 16| 8| 4| 2| 1|     
-------------------------------------------
|      $a    |   0|  0|  0|  0| 1| 0| 0| 1|    
-------------------------------------------
|      $b    |   0|  0|  0|  0| 1| 0| 1| 0|
------------------------------------------- 
|      &     |   0|  0|  0|  0| 1| 0| 0| 0|
-------------------------------------------

So you can see from the table the only bit they share together is the 8 bit.

Second example

$a =  36;
$b = 103;
echo $a & $b; // This would output the number 36.
$a = 00100100
$b = 01100111

The two shared bits are 32 and 4, which when added together return 36.

The "Or" operator: `|`

$a =  9;
$b = 10;
echo $a | $b;

This would output the number 11. Why?

-------------------------------------------
|      1 Byte ( 8 bits )                  |
-------------------------------------------
|Place Value | 128| 64| 32| 16| 8| 4| 2| 1|     
-------------------------------------------
|      $a    |   0|  0|  0|  0| 1| 0| 0| 1|    
-------------------------------------------
|      $b    |   0|  0|  0|  0| 1| 0| 1| 0|
------------------------------------------- 
|      |     |   0|  0|  0|  0| 1| 0| 1| 1|
-------------------------------------------

You will notice that we have 3 bits set, in the 8, 2, and 1 columns. Add those up: 8+2+1=11.

13 revs, 6 users 79% · Accepted Answer · 2021-09-09 15:16:55Z

378

`<=>` Spaceship Operator

Added in PHP 7

The spaceship operator <=> is the latest comparison operator added in PHP 7. It is a non-associative binary operator with the same precedence as equality operators (==, !=, ===, !==). This operator allows for simpler three-way comparison between left-hand and right-hand operands.

The operator results in an integer expression of:

0 when both operands are equal
Less than 0 when the left-hand operand is less than the right-hand operand
Greater than 0 when the left-hand operand is greater than the right-hand operand

e.g.

1 <=> 1; // 0
1 <=> 2; // -1
2 <=> 1; // 1

A good practical application of using this operator would be in comparison type callbacks that are expected to return a zero, negative, or positive integer based on a three-way comparison between two values. The comparison function passed to usort is one such example.

Before PHP 7 you would write...

$arr = [4,2,1,3];

usort($arr, function ($a, $b) {
    if ($a < $b) {
        return -1;
    } elseif ($a > $b) {
        return 1;
    } else {
        return 0;
    }
});

Since PHP 7 you can write...

$arr = [4,2,1,3];

usort($arr, function ($a, $b) {
    return $a <=> $b;
    // return $b <=> $a; // for reversing order
});

edited Sep 9, 2021 at 15:16

community wiki

13 revs, 6 users 79%
Sherif

28

Not sure how $a <=> $b is different to $a - $b
– rev
Commented Aug 28, 2015 at 17:37
52

@AcidShout $a - $b works for numbers, but not strings, objects, or arrays.
– mcrumley
Commented Sep 25, 2015 at 18:29
69

@mcrumley No, it's worse than that. In general $a - $b doesn't even work for numbers; it works only for integers. It doesn't work for non-integer numbers, because usort casts your comparator function's return values to int, which means 0.5 gets cast to 0, which means that two numbers with a difference of less than 1, such as 4 and 4.6, may (depending upon which one gets passed as the first argument to your comparator function) incorrectly compare as equal.
– Mark Amery
Commented Nov 5, 2015 at 15:54
6

@MarkAmery the migration guide isn't the documented behavior of the operator. For that you want to look at the language operators section of the manual for that php.net/language.operators.comparison the actual behavior behind this relies on various comparison functions of the API, like when you're doing strcmp for strings, where you can not guarantee the actual return value in every single case. Sure, it's almost always 1, 0, or -1, but for the cases where you can't guarantee it like in wrapping libc's strcmp, you offer up the same defined behavior as the underlying spec to be safe
– Sherif
Commented Jan 20, 2016 at 22:45
15

@MarkAmery The point here is not to allow people to rely on undefined behavior. For the one case where someones gets a value that is not exactly 1, 0, or -1, you get someone filing a bug report thinking there's something wrong in the language. Which is why we document that all we can guarantee is that value will be less than, greater than, or equal to 0, and not necessarily 1, 0, and -1.
– Sherif
Commented Jan 20, 2016 at 22:50

| Show 4 more comments

4 revs, 4 users 75% · Accepted Answer · 2018-02-19 08:14:39Z

319

_ Alias for gettext()

The underscore character '_' as in _() is an alias to the gettext() function.

edited Feb 19, 2018 at 8:14

community wiki

4 revs, 4 users 75%
Habeeb Perwad

Any idea what the double underscore function is? __(). It is used in WordPress. I cannot find a definition for it anywhere. Example of its use: core.trac.wordpress.org/browser/tags/5.4/src/wp-admin/includes/…. It seems that to use the WP image_size_names_choose() filter, __() must be used to add the "short name" to the array of named_sizes you want to add.
– SherylHohman
Commented Jul 1, 2020 at 1:54
2

@SherylHohman Look like it is translation function. developer.wordpress.org/reference/functions/__
– Mohammed H
Commented Jul 2, 2020 at 3:08

Add a comment |

10 revs, 10 users 20% · Accepted Answer · 2021-07-07 17:59:50Z

Syntax	Name	Description
`x == y`	Equality	`true` if x and y have the same key/value pairs
`x != y`	Inequality	`true` if x is not equal to y
`x === y`	Identity	`true` if x and y have the same key/value pairs in the same order and of the same types
`x !== y`	Non-identity	`true` if x is not identical to y
`x <=> y`	Spaceship	0 if x is equal to y, greater than 0 if x > y, less than 0 if x < y
`++x`	Pre-increment	Increments x by one, then returns x
`x++`	Post-increment	Returns x, then increments x by one
`--x`	Pre-decrement	Decrements x by one, then returns x
`x--`	Post-decrement	Returns x, then decrements x by one
`x and y`	And	`true` if both x and y are `true`. If x=6, y=3 then `(x < 10 and y > 1)` returns `true`
`x && y`	And	`true` if both x and y are `true`. If x=6, y=3 then `(x < 10 && y > 1)` returns `true`
`x or y`	Or	`true` if any of x or y are `true`. If x=6, y=3 then `(x < 10 or y > 10)` returns `true`
`x \|\| y`	Or	`true` if any of x or y are `true`. If x=6, y=3 then `(x < 3 \|\| y > 1)` returns `true`
`a . b`	Concatenation	Concatenate two strings: "Hi" . "Ha"

2 revs, 2 users 66% · Accepted Answer · 2014-02-21 00:42:41Z

Magic constants: Although these are not just symbols but important part of this token family. There are eight magical constants that change depending on where they are used.

__LINE__: The current line number of the file.

__FILE__: The full path and filename of the file. If used inside an include, the name of the included file is returned. Since PHP 4.0.2, __FILE__ always contains an absolute path with symlinks resolved whereas in older versions it contained relative path under some circumstances.

__DIR__: The directory of the file. If used inside an include, the directory of the included file is returned. This is equivalent to dirname(__FILE__). This directory name does not have a trailing slash unless it is the root directory. (Added in PHP 5.3.0.)

__FUNCTION__: The function name. (Added in PHP 4.3.0) As of PHP 5 this constant returns the function name as it was declared (case-sensitive). In PHP 4 its value is always lowercased.

__CLASS__: The class name. (Added in PHP 4.3.0) As of PHP 5 this constant returns the class name as it was declared (case-sensitive). In PHP 4 its value is always lowercased. The class name includes the namespace it was declared in (e.g. Foo\Bar). Note that as of PHP 5.4 __CLASS__ works also in traits. When used in a trait method, __CLASS__ is the name of the class the trait is used in.

__TRAIT__: The trait name. (Added in PHP 5.4.0) As of PHP 5.4 this constant returns the trait as it was declared (case-sensitive). The trait name includes the namespace it was declared in (e.g. Foo\Bar).

__METHOD__: The class method name. (Added in PHP 5.0.0) The method name is returned as it was declared (case-sensitive).

__NAMESPACE__: The name of the current namespace (case-sensitive). This constant is defined in compile-time (Added in PHP 5.3.0).

Source

3 revs, 3 users 51% · Accepted Answer · 2016-03-13 01:16:00Z

Type Operators

instanceof is used to determine whether a PHP variable is an instantiated object of a certain class.

<?php
class mclass { }
class sclass { }
$a = new mclass;
var_dump($a instanceof mclass);
var_dump($a instanceof sclass);

The above example will output:

bool(true)
bool(false)

Reason: Above Example $a is a object of the mclass so use only a mclass data not instance of with the sclass

Example with inheritance

<?php 
class pclass { } 
class childclass extends pclass { } 
$a = new childclass; 
var_dump($a instanceof childclass); 
var_dump($a instanceof pclass);

The above example will output:

bool(true)
bool(true)

Example with Clone

<?php 
class cloneable { } 
$a = new cloneable;
$b = clone $a; 
var_dump($a instanceof cloneable); 
var_dump($b instanceof cloneable);

The above example will output:

bool(true)
bool(true)

The above works with 'interfaces' as well. This is useful for checking that a particular interface is available. — Ryan Vincent, Commented Feb 24, 2014 at 11:38

15 revs, 10 users 86% · Accepted Answer · 2023-02-22 22:05:24Z

An overview of operators in PHP:

Logical Operators:

$a && $b : TRUE if both $a and $b are TRUE.
$a || $b : TRUE if either $a or $b is TRUE.
$a xor $b : TRUE if either $a or $b is TRUE, but not both.
! $a : TRUE if $a is not TRUE.
$a and $b : TRUE if both $a and $b are TRUE.
$a or $b : TRUE if either $a or $b is TRUE.

Comparison operators:

$a == $b : TRUE if $a is equal to $b after type juggling.
$a === $b : TRUE if $a is equal to $b, and they are of the same type.
$a != $b : TRUE if $a is not equal to $b after type juggling.
$a <> $b : TRUE if $a is not equal to $b after type juggling.
$a !== $b : TRUE if $a is not equal to $b, or they are not of the same type.
$a < $b : TRUE if $a is strictly less than $b.
$a > $b : TRUE if $a is strictly greater than $b.
$a <= $b : TRUE if $a is less than or equal to $b.
$a >= $b : TRUE if $a is greater than or equal to $b.
$a <=> $b : An integer less than, equal to, or greater than zero when $a is respectively less than, equal to, or greater than $b. Available as of PHP 7.
$a ? $b : $c : if $a return $b else return $c (ternary operator)
$a ?? $c : Same as $a ? $a : $c (null coalescing operator - requires PHP>=7)

Arithmetic Operators:

-$a : Opposite of $a.
$a + $b : Sum of $a and $b.
$a - $b : Difference of $a and $b.
$a * $b : Product of $a and $b.
$a / $b : Quotient of $a and $b.
$a % $b : Remainder of $a divided by $b.
$a ** $b : Result of raising $a to the $b'th power (introduced in PHP 5.6)

Incrementing/Decrementing Operators:

++$a : Increments $a by one, then returns $a.
$a++ : Returns $a, then increments $a by one.
--$a : Decrements $a by one, then returns $a.
$a-- : Returns $a, then decrements $a by one.

Bitwise Operators:

$a & $b : Bits that are set in both $a and $b are set.
$a | $b : Bits that are set in either $a or $b are set.
$a ^ $b : Bits that are set in $a or $b but not both are set.
~ $a : Bits that are set in $a are not set, and vice versa.
$a << $b : Shift the bits of $a $b steps to the left (each step means "multiply by two")
$a >> $b : Shift the bits of $a $b steps to the right (each step means "divide by two")

String Operators:

$a . $b : Concatenation of $a and $b.

Array Operators:

$a + $b : Union of $a and $b.
$a == $b : TRUE if $a and $b have the same key/value pairs.
$a === $b : TRUE if $a and $b have the same key/value pairs in the same order and of the same types.
$a != $b : TRUE if $a is not equal to $b.
$a <> $b : TRUE if $a is not equal to $b.
$a !== $b : TRUE if $a is not identical to $b.

Assignment Operators:

$a = $b : The value of $b is assigned to $a
$a += $b : Same as $a = $a + $b
$a -= $b : Same as $a = $a - $b
$a *= $b : Same as $a = $a * $b
$a /= $b : Same as $a = $a / $b
$a %= $b : Same as $a = $a % $b
$a **= $b : Same as $a = $a ** $b
$a .= $b : Same as $a = $a . $b
$a &= $b : Same as $a = $a & $b
$a |= $b : Same as $a = $a | $b
$a ^= $b : Same as $a = $a ^ $b
$a <<= $b : Same as $a = $a << $b
$a >>= $b : Same as $a = $a >> $b
$a ??= $b : The value of $b is assigned to $a if $a is null or not defined (null coalescing assignment operator - requires PHP>=7.4)

Note

and operator and or operator have lower precedence than assignment operator =.

This means that $a = true and false; is equivalent to ($a = true) and false.

In most cases you will probably want to use && and ||, which behave in a way known from languages like C, Java or JavaScript.

There is an error in $a ?? $c, it says is the same as $a ? $a : $c, but ternary operator checks if value is true, on the other hand, null coalescing checks for null values, so, if $a is 0, you will get 0 (because 0 is not null), for example if you have: $a=0; $c=5; then $a?$a:$c returns 5, and $a??$c returns 0. — stramin, Commented Jul 29, 2019 at 18:41

6 revs, 4 users 93% · Accepted Answer · 2020-06-20 09:12:55Z

Spaceship Operator `<=>` (Added in PHP 7)

Examples for <=> Spaceship operator (PHP 7, Source: PHP Manual):

Integers, Floats, Strings, Arrays & objects for Three-way comparison of variables.

// Integers
echo 10 <=> 10; // 0
echo 10 <=> 20; // -1
echo 20 <=> 10; // 1

// Floats
echo 1.5 <=> 1.5; // 0
echo 1.5 <=> 2.5; // -1
echo 2.5 <=> 1.5; // 1

// Strings
echo "a" <=> "a"; // 0
echo "a" <=> "b"; // -1
echo "b" <=> "a"; // 1
// Comparison is case-sensitive
echo "B" <=> "a"; // -1

echo "a" <=> "aa"; // -1
echo "zz" <=> "aa"; // 1

// Arrays
echo [] <=> []; // 0
echo [1, 2, 3] <=> [1, 2, 3]; // 0
echo [1, 2, 3] <=> []; // 1
echo [1, 2, 3] <=> [1, 2, 1]; // 1
echo [1, 2, 3] <=> [1, 2, 4]; // -1

// Objects
$a = (object) ["a" => "b"]; 
$b = (object) ["a" => "b"]; 
echo $a <=> $b; // 0

$a = (object) ["a" => "b"]; 
$b = (object) ["a" => "c"]; 
echo $a <=> $b; // -1

$a = (object) ["a" => "c"]; 
$b = (object) ["a" => "b"]; 
echo $a <=> $b; // 1

// only values are compared
$a = (object) ["a" => "b"]; 
$b = (object) ["b" => "b"]; 
echo $a <=> $b; // 1

2 revs · Accepted Answer · 2017-05-23 12:02:56Z

92

{} Curly braces

And some words about last post

$x[4] = 'd'; // it works
$x{4} = 'd'; // it works

$echo $x[4]; // it works
$echo $x{4}; // it works

$x[] = 'e'; // it works
$x{} = 'e'; // does not work

$x = [1, 2]; // it works
$x = {1, 2}; // does not work

echo "${x[4]}"; // it works
echo "${x{4}}"; // does not work

echo "{$x[4]}"; // it works
echo "{$x{4}}"; // it works

edited May 23, 2017 at 12:02

community wiki

2 revs
mnv

5

{''} notation for property names. echo $movies->movie->{'great-lines'}->line; can be used to access data in SimpleXMLElement. Maybe it can be used in other cases too. php.net/manual/en/simplexml.examples-basic.php
– Andrei
Commented Sep 5, 2017 at 12:15

Add a comment |

3 revs, 3 users 94% · Accepted Answer · 2018-02-16 14:14:48Z

Null coalescing operator (??)

This operator has been added in PHP 7.0 for the common case of needing to use a ternary operator in conjunction with isset(). It returns its first operand if it exists and is not NULL; otherwise it returns its second operand.

<?php
// Fetches the value of $_GET['user'] and returns 'nobody'
// if it does not exist.
$username = $_GET['user'] ?? 'nobody';
// This is equivalent to:
$username = isset($_GET['user']) ? $_GET['user'] : 'nobody';

// Coalescing can be chained: this will return the first
// defined value out of $_GET['user'], $_POST['user'], and
// 'nobody'.
$username = $_GET['user'] ?? $_POST['user'] ?? 'nobody';
?>

3 revs, 3 users 90% · Accepted Answer · 2016-02-02 13:13:06Z

84

PHP Strings: PHP Strings can be specified in four ways not just two ways:

1) Single Quote Strings:

$string = 'This is my string'; // print This is my string

2) Double Quote Strings:

$str = 'string';

$string = "This is my $str"; // print This is my string

3) Heredoc:

$string = <<<EOD
This is my string
EOD; // print This is my string

4) Nowdoc (since PHP 5.3.0):

$string = <<<'END_OF_STRING'
    This is my string 
END_OF_STRING; // print This is my string

edited Feb 2, 2016 at 13:13

community wiki

3 revs, 3 users 90%
devpro

Add a comment |

4 revs, 2 users 63% · Accepted Answer · 2020-12-07 10:03:37Z

QUESTION:

What does => mean?

ANSWER:

=> Is the symbol we humans decided to use to separate "Key" => "Value" pairs in Associative Arrays.

ELABORATING:

To understand this, we have to know what Associative Arrays are. The first thing that comes up when a conventional programmer thinks of an array (in PHP) would be something similar to:

$myArray1 = array(2016, "hello", 33);//option 1

$myArray2 = [2016, "hello", 33];//option 2

$myArray3 = [];//option 3
$myArray3[] = 2016; 
$myArray3[] = "hello"; 
$myArray3[] = 33;

Where as, if we wanted to call the array in some later part of the code, we could do:

echo $myArray1[1];// output: hello
echo $myArray2[1];// output: hello
echo $myArray3[1];// output: hello

So far so good. However, as humans, we might find it hard to remember that index [0] of the array is the value of the year 2016, index [1] of the array is a greetings, and index [2] of the array is a simple integer value. The alternative we would then have is to use what is called an Associative Array. An Associative array has a few differences from a Sequential Array (which is what the previous cases were since they increment the index used in a predetermined sequence, by incrementing by 1 for each following value).

Differences (between a sequential and associative array):

Durring the declaration of an Associative Array, you don't only include the value of what you want to put in the array, but you also put the index value (called the key) which you want to use when calling the array in later parts of the code. The following syntax is used during it's declaration: "key" => "value".
When using the Associative Array, the key value would then be placed inside the index of the array to retrieve the desired value.

For instance:

$myArray1 = array( 
    "Year" => 2016, 
    "Greetings" => "hello", 
    "Integer_value" => 33);//option 1

$myArray2 = [ 
    "Year" =>  2016, 
    "Greetings" => "hello", 
    "Integer_value" => 33];//option 2

$myArray3 = [];//option 3
$myArray3["Year"] = 2016; 
$myArray3["Greetings"] = "hello"; 
$myArray3["Integer_value"] = 33;

And now, to receive the same output as before, the key value would be used in the arrays index:

echo $myArray1["Greetings"];// output: hello
echo $myArray2["Greetings"];// output: hello
echo $myArray3["Greetings"];// output: hello

FINAL POINT:

So from the above example, it is pretty easy to see that the => symbol is used to express the relationship of an Associative Array between each of the key and value pairs in an array DURING the initiation of the values within the array.

2 revs · Accepted Answer · 2017-03-20 05:37:15Z

Question:

What does "&" mean here in PHP?

PHP "&" operator

Makes life more easier once we get used to it..(check example below carefully)

& usually checks bits that are set in both $a and $b are set.

have you even noticed how these calls works?

   error_reporting(E_ERROR | E_WARNING | E_PARSE);
    error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE);
    error_reporting(E_ALL & ~E_NOTICE);
    error_reporting(E_ALL);

So behind all above is game of bitwise operator and bits.

One usefull case of these is easy configurations like give below, so a single integer field can store thousands of combos for you.

Most people have already read the docs but didn't reliase the real world use case of these bitwise operators.

Example That you 'll love

<?php

class Config {

    // our constants must be 1,2,4,8,16,32,64 ....so on
    const TYPE_CAT=1;
    const TYPE_DOG=2;
    const TYPE_LION=4;
    const TYPE_RAT=8;
    const TYPE_BIRD=16;
    const TYPE_ALL=31;

    private $config;

    public function __construct($config){
        $this->config=$config;

        if($this->is(Config::TYPE_CAT)){
            echo 'cat ';
        }
        if($this->is(Config::TYPE_DOG)){
            echo 'dog ';
        }
        if($this->is(Config::TYPE_RAT)){
            echo 'rat ';
        }
        if($this->is(Config::TYPE_LION)){
            echo 'lion ';
        }
        if($this->is(Config::TYPE_BIRD)){
            echo 'bird ';
        }
        echo "\n";
    }

    private function is($value){
        return $this->config & $value;
    }
}

new Config(Config::TYPE_ALL);
// cat dog rat lion bird
new Config(Config::TYPE_BIRD);
//bird
new Config(Config::TYPE_BIRD | Config::TYPE_DOG);
//dog bird
new Config(Config::TYPE_ALL & ~Config::TYPE_DOG & ~Config::TYPE_CAT);
//rat lion bird

3 revs, 3 users 74% · Accepted Answer · 2020-06-20 09:12:55Z

47

== is used for check equality without considering variable data-type

=== is used for check equality for both the variable value and data-type

Example

$a = 5

if ($a == 5) - will evaluate to true
if ($a == '5') - will evaluate to true, because while comparing this both value PHP internally convert that string value into integer and then compare both values
if ($a === 5) - will evaluate to true
if ($a === '5') - will evaluate to false, because value is 5, but this value 5 is not an integer.

edited Jun 20, 2020 at 9:12

community wiki

3 revs, 3 users 74%
Parth Nayak

Add a comment |

Yogi Ghorecha · Accepted Answer · 2017-12-06 16:05:51Z

Null Coalesce operator "??" (Added in PHP 7)

Not the catchiest name for an operator, but PHP 7 brings in the rather handy null coalesce so I thought I'd share an example.

In PHP 5, we already have a ternary operator, which tests a value, and then returns the second element if that returns true and the third if it doesn't:

echo $count ? $count : 10; // outputs 10

There is also a shorthand for that which allows you to skip the second element if it's the same as the first one: echo $count ?: 10; // also outputs 10

In PHP 7 we additionally get the ?? operator which rather than indicating extreme confusion which is how I would usually use two question marks together instead allows us to chain together a string of values. Reading from left to right, the first value which exists and is not null is the value that will be returned.

// $a is not set
$b = 16;

echo $a ?? 2; // outputs 2
echo $a ?? $b ?? 7; // outputs 16

This construct is useful for giving priority to one or more values coming perhaps from user input or existing configuration, and safely falling back on a given default if that configuration is missing. It's kind of a small feature but it's one that I know I'll be using as soon as my applications upgrade to PHP 7.

2 revs, 2 users 95% · Accepted Answer · 2019-05-01 08:17:41Z

Nullable return type declaration

PHP 7 adds support for return type declarations. Similarly to argument type declarations, return type declarations specify the type of value that will be returned from a function. The same types are available for return type declarations as are available for argument type declarations.

Strict typing also has an effect on return type declarations. In the default weak mode, returned values will be coerced to the correct type if they are not already of that type. In strong mode, the returned value must be of the correct type, otherwise, a TypeError will be thrown.

As of PHP 7.1.0, return values can be marked as nullable by prefixing the type name with a question mark (?). This signifies that the function returns either the specified type or NULL.

<?php
function get_item(): ?string {
    if (isset($_GET['item'])) {
        return $_GET['item'];
    } else {
        return null;
    }
}
?>

Source

2 revs, 2 users 73% · Accepted Answer · 2022-07-03 01:36:04Z

Three DOTS as Splat Operator (...) (since PHP 5.6)

PHP has an operator "..." (Three dots) which is referred as Splat Operator. It is used to pass arbitrary number of parameters in a function and this type of function is called Variadic Functions. Let’s take examples to use of "..." (Three dots).

Example 1:

<?php
function calculateNumbers(...$params){
    $total = 0;
    foreach($params as $v){
        $total = $total + $v;
    }
    return $total;
}
 
echo calculateNumbers(10, 20, 30, 40, 50);
 
//Output 150
?>

Each arguments of calculateNumbers() function pass through $params as an array when use "… ".

There are many different ways to use "… " operator. Below some examples:

Example 2:

<?php
function calculateNumbers($no1, $no2, $no3, $no4, $no5){
    $total = $no1 + $no2 + $no3 + $no4 + $no5;
    return $total;
}
 
$numbers = array(10, 20, 30, 40, 50);
echo calculateNumbers(...$numbers);
 
//Output 150
?>

Example 3:

<?php
function calculateNumbers(...$params){
    $total = 0;
    foreach($params as $v){
        $total = $total + $v;
    }
    return $total;
}
$no1 = 70;
$numbers = array(10, 20, 30, 40, 50);
echo calculateNumbers($no1, ...$numbers);
 
//Output 220
?>

Example 4:

<?php
function calculateNumbers(...$params){
    $total = 0;
    foreach($params as $v){
        $total = $total + $v;
    }
    return $total;
}
 
$numbers1 = array(10, 20, 30, 40, 50);
$numbers2 = array(100, 200, 300, 400, 500);
echo calculateNumbers(...$numbers1, ...$numbers2);
 
//Output 1650
 
?>

It should be noted that Variadic Parameters cannot be targeted by named arguments.

Example 5:

<?php
function sumIntegers(int ...$params): int {
    $sum = 0;
    foreach($params as $value){
        $sum += $value;
    }
    return $sum;
}


echo sumIntegers(params: [1, 2, 3, 4]);     
// $params will be equal to ['params' => [1, 2, 3, 4]] in sumIntegers
// throws TypeError sumIntegers(): Argument #1 must be of type int, array given 

echo sumIntegers(arbitrary_name: 1, another_name: 2);
// $params will be equal to ['arbitrary_name' => 1, 'another_name' => 2] in sumIntegers
// Outputs: 3 
?>

Using an unpacked associative array as the parameter for a function call has the same effect as calling the function using each key-value pair as a named argument.

Example 6:

<?php
function fullName(string $first_name, ?string $middle_name = null, ?string $last_name = null): string {
    return trim("$first_name|$middle_name|$last_name");
}

$params = ['first_name' => 'John', 'last_name' => 'Doe'];
echo fullName(...$params);
// same as fullName(first_name: 'John', last_name: 'Doe')

// outputs 'John||Doe'
?>

This can be used to pass named arguments to something like a nested function call or a class.

Example 7:

<?php
function throw_exception(string $exception, ...$parameters) {
    throw new $exception(...$parameters);
}

throw_exception(exception: 'Exception', code: 123);
// executes throw new Exception(...['code' => 123])
// which is the same as throw new Exception(code: 123);
?>

5 revs, 3 users 63% · Accepted Answer · 2024-07-31 22:14:42Z

`?->` Nullsafe Operator

Added in PHP 8.0

The nullsafe operator returns null in case you try to invoke functions or get values from null. The nullsafe operator can be chained and can be used both on the methods and properties.

$objDrive = null;
$drive = $objDrive?->func?->getDriver()?->value; //return null
$drive = $objDrive->func->getDriver()->value; // Error: Trying to get property 'func' of non-object

It doesn't work with array keys:

$drive['admin']?->getDriver()?->value //Warning: Trying to access array offset on value of type null

$drive = [];
$drive['admin']?->getAddress()?->value //Warning: Undefined array key "admin"

mdfst13 · Accepted Answer · 2022-03-28 02:28:24Z

#[] attributes since PHP 8

You can write #[attribute_name] since PHP 8. This is an attribute in PHP (also Rust and C#). Other languages may use names like annotations (Java) or decorators (Python, Javascript) for a similar feature. Prior to PHP 8, #[whatever] would have been a comment until the end of the line (because # starts a comment in PHP). So if an attribute is the last thing on a line, it will be ignored in versions before PHP 8. If not the last thing on a line, it would comment out whatever was after it prior to PHP 8 (since then the ] terminates it).

RFC
Syntax RFC (the syntax was changed from the original RFC)
Documentation

2 revs, 2 users 80% · Accepted Answer · 2022-01-23 01:26:20Z

In php 8

Instead of writing the classic !== null you can use the ? operator to write just 1 line of code, the code becomes pretty clear:

Before:

$firsName =  null;
if ($session !== null) {
    $user = $session->user;
    if ($user !== null) {
        $name = $user->getName();
        if ($name !== null) {
            $firstName = $name->firstName;
        }
    }
}

After:

$firsName = $session?->user?->getName()?->firstName;

Use match instead of switch. The match expression uses strict comparison (===) instead. The comparison is strict regardless of strict_types.

Before:

switch ('A') {
    case 'A':
        echo "found A";
        break;
    case 'B':
        echo "found B";
        break;
}
// Result: "found A"

After:

echo match ('A') {
  'A' => "found A",
  'B' => "found B",
};
// Result: "found A"

mickmackusa · Accepted Answer · 2022-07-05 07:09:17Z

4

Double-dot syntax

When used between two characters in qualifying native PHP string functions, .. acts to express an inclusive range of characters. a-e is equivalent to abcde.

echo trim('adobe', 'a..e');

Prints:

Native PHP functions that allow double-dot range syntax

answered Jul 5, 2022 at 7:09

community wiki

mickmackusa

Add a comment |

Seaworn · Accepted Answer · 2023-03-08 21:07:19Z

2

Answer recommended by PHP Collective

First class callable syntax (PHP 8.1)

The ellipsis (...) has gained another use introduced in PHP8.1 to create an anonymous function from a callable

Before PHP 8.1

$callable = [$instance, 'someMethod'];

In PHP 8.1

$callable = $instance->someMethod(...);

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The List

24 Answers 24

Bitwise Operator

A few examples for better understanding

The "AND" operator: &

The "Or" operator: |

<=> Spaceship Operator

Added in PHP 7

Before PHP 7 you would write...

Since PHP 7 you can write...

Type Operators

Example with inheritance

Example with Clone

An overview of operators in PHP:

Note

Spaceship Operator <=> (Added in PHP 7)

PHP "&" operator

Example That you 'll love

Example

Null Coalesce operator "??" (Added in PHP 7)

Nullable return type declaration

Three DOTS as Splat Operator (...) (since PHP 5.6)

?-> Nullsafe Operator

#[] attributes since PHP 8

Double-dot syntax

Not the answer you're looking for? Browse other questions tagged phpargumentsoperatorssymbolssemantics or ask your own question.

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Related

The "AND" operator: `&`

The "Or" operator: `|`

`<=>` Spaceship Operator

Spaceship Operator `<=>` (Added in PHP 7)

`?->` Nullsafe Operator

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