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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(=> "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.

PHP Manual