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# array_filter

(PHP 4 >= 4.0.6, PHP 5)

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

## Description

array array_filter ( array input [, callback callback])

array_filter() iterates over each value in the `input` array passing them to the `callback` function. If the `callback` function returns true, the current value from `input` is returned into the result array. Array keys are preserved.

Example 1. array_filter() example
`<?php 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.

If the `callback` function is not supplied, array_filter() will remove all the entries of `input` that are equal to `FALSE`. See converting to boolean for more information.

Example 2. array_filter() without `callback`
`<?php $entry = array( 0 => 'foo', 1 => false, 2 => -1, 3 => null, 4 => '' ); print_r(array_filter($entry)); ?>`
This will output :
    Array
    (
        [0] => foo
        [2] => -1
    )

See also array_map(), array_reduce(), and array_walk().

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