uksort

(PHP 4, PHP 5, PHP 7)

Sort an array by keys using a user-defined comparison function

bool uksort ( array &$array, callable $key_compare_func )

uksort() will sort the keys of an array using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function.

Parameters:

array

The input array.

key_compare_func

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

int callback ( mixed $a, mixed $b )

Returns:

Returns TRUE on success or FALSE on failure.

Examples:

uksort() example

<?php
function cmp($a, $b)
{
    $a = preg_replace('@^(a|an|the) @', '', $a);
    $b = preg_replace('@^(a|an|the) @', '', $b);
    return strcasecmp($a, $b);
}

$a = array("John" => 1, "the Earth" => 2, "an apple" => 3, "a banana" => 4);

uksort($a, "cmp");

foreach ($a as $key => $value) {
    echo "$key: $value\n";
}
?>

The above example will output:

an apple: 3
a banana: 4
the Earth: 2
John: 1