PHP 4, PHP 5, PHP 7, PHP 8
uasort - Sort an array with a user-defined comparison function and maintain index association
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uasort( arrayarray, callable$callback ): bool

Sorts array in place such that its keys maintain their correlation with the values they are associated with, using a user-defined comparison function.

This is used mainly when sorting associative arrays where the actual element order is significant.


If two members compare as equal, they retain their original order. Prior to PHP 8.0.0, their relative order in the sorted array was undefined.


Resets array's internal pointer to the first element.



The input array.


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.

callback(mixed$a,mixed$b ): int

Return Values

Always returns true.


Version Description
8.0.0 If callback expects a parameter to be passed by reference, this function will now emit an E_WARNING.

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