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PHP Manual

## Array Operators

Array Operators
Example | Name | Result
--- | --- | ---
$a + $b | Union | Union of $a and $b.
$a == $b | Equality | `TRUE` if $a and $b have the same key/value pairs.
$a === $b | Identity | `TRUE` if $a and $b have the same key/value pairs in the same order and of the same types.
$a != $b | Inequality | `TRUE` if $a is not equal to $b.
$a <> $b | Inequality | `TRUE` if $a is not equal to $b.
$a !== $b | Non-identity | `TRUE` if $a is not identical to $b.

The + operator returns the right-hand array appended to the left-hand array; for keys that exist in both arrays, the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored.

`<?php
$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");
$c = $a + $b; // Union of $a and $b
echo "Union of \$a and \$b: \n";
var_dump($c);
$c = $b + $a; // Union of $b and $a
echo "Union of \$b and \$a: \n";
var_dump($c);
?>`
When executed, this script will print the following:

    Union of $a and $b:
    array(3) {
      ["a"]=>
      string(5) "apple"
      ["b"]=>
      string(6) "banana"
      ["c"]=>
      string(6) "cherry"
    }
    Union of $b and $a:
    array(3) {
      ["a"]=>
      string(4) "pear"
      ["b"]=>
      string(10) "strawberry"
      ["c"]=>
      string(6) "cherry"
    }

Elements of arrays are equal for the comparison if they have the same key and value.

Example #1 Comparing arrays

`<?php
$a = array("apple", "banana");
$b = array(1 => "banana", "0" => "apple");
var_dump($a == $b); // bool(true)
var_dump($a === $b); // bool(false)
?>`

See also the manual sections on the Array type and Array functions.

String Operators
Type Operators
Operators
PHP Manual