(PHP 4 >= 4.0.1, PHP 5, PHP 7)
array_diff — Computes the difference of arrays
array1 against one or more other arrays and
returns the values in
array1 that are not present in
any of the other arrays.
The array to compare from
An array to compare against
More arrays to compare against
Returns an array containing all the entries from
array1 that are not present in any of the other arrays.
Example #1 array_diff() example
$array1 = array("a" => "green", "red", "blue", "red");
$array2 = array("b" => "green", "yellow", "red");
$result = array_diff($array1, $array2);
Multiple occurrences in $array1 are all treated the same way. This will output :
Array (  => blue )
Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is the same.
This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using array_diff($array1, $array2);.