usort

Synopsis

Returns

TRUE on success; FALSE on error

Description

usort() sorts array according to the user-defined function named by func . This can be useful for doing sorts with custom algorithms or doing non-case-sensitive sorts with alphabetic characters. When you pass usort() an array and the name of a user-defined function, it uses the bubblesort method and traverses the elements of the array to sort them. The custom function must return -1, 0, or 1 for this method to work correctly (see example). If used on an associative array, this function causes the keys to be destroyed while sorting on the values.

func should be written to accept two parameters, which it compares. If they're considered equivalent, 0 should be returned. If the first is considered to be greater, 1 should be returned. If the second is considered to be greater, -1 should be returned.

Version

PHP 3 since 3.0.3, PHP 4

See also

See also array_multisort() , arsort() , asort() , krsort() , ksort() , natsort() , natcasesort() , rsort() , sort() , uasort() , uksort()

Example

function usort_cmp($a, $b) {
   if ($a == $b) return 0;
   return ($a > $b) ? -1 : 1;
}

$arr = array("Banana", "carrot",
             "Apple", "banana",
             "apple", "Carrot");
usort($arr, "usort_cmp");
while(list($k, $v) = each($arr)) {
   echo "$k => $v\n";
}

Output:
0 => Apple
1 => Banana
2 => Carrot
3 => apple
4 => banana
5 => carrot