PHP has several functions that deal with sorting arrays, and this document exists to help sort it all out. The main differences are: Some sort based on the array keys, whereas others by the values: $array['key'] = 'value'; Whether or not the correlation between the keys and values are maintained after the sort, which may mean the keys are reset numerically (0,1,2 ...) The order of the sort: alphabetical, low to high (ascending), high to low (descending), numerical, natural, random, or user defined Note: All of these sort functions act directly on the array variable itself, as opposed to returning a new sorted array If any of these sort functions evaluates two members as equal then the order is undefined (the sorting is not stable). Function name Sorts by Maintains key association Order of sort Related functions array_multisort value associative yes, numeric no first array or sort options array_walk asort value yes low to high arsort arsort value yes high to low asort krsort key yes high to low ksort ksort key yes low to high asort natcasesort value yes natural, case insensitive natsort natsort value yes natural natcasesort rsort value no high to low sort shuffle value no random array_rand sort value no low to high rsort uasort value yes user defined uksort uksort key yes user defined uasort usort value no user defined uasort