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# array_filter

(PHP 4 >= 4.0.6)

array_filter -- Filters elements of an array using a callback function

## Description

array array_filter ( array input [, callback function])

array_filter() returns an array containing all the elements of `input` filtered according a callback `function`. If the `input` is an associative array the keys are preserved.

Example 1. array_filter() example
    function odd($var) {
        return ($var % 2 == 1);
    }

    function even($var) {
        return ($var % 2 == 0);
    }

    $array1 = array ("a"=>1, "b"=>2, "c"=>3, "d"=>4, "e"=>5);
    $array2 = array (6, 7, 8, 9, 10, 11, 12);

    echo "Odd :\n";
    print_r(array_filter($array1, "odd"));
    echo "Even:\n";
    print_r(array_filter($array2, "even"));
The printout of the program above will be:
    Odd :
    Array
    (
        [a] => 1
        [c] => 3
        [e] => 5
    )
    Even:
    Array
    (
        [0] => 6
        [2] => 8
        [4] => 10
        [6] => 12
    )

Users may not change the array itself from the callback function. e.g. Add/delete an element, unset the array that array_filter() is applied to. If the array is changed, the behavior of this function is undefined.

See also array_map() and array_reduce().

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