Sorting keys, records, and ties

The idea

PHP arrays are ordered maps, so sorting can change both traversal order and key handling. sort orders values and reindexes numeric keys, while asort preserves key associations as it orders values. A record list often needs usort with an explicit comparator. Choose the operation by deciding whether keys identify records or merely represent their current positions.

A comparator should return a negative value, zero, or a positive value according to the intended order. The spaceship operator expresses this comparison directly for suitable values. Add a secondary key when ties must be deterministic, such as score followed by identifier. Sorting changes the supplied array variable, so make an ordinary array copy first if the caller’s order must remain unchanged, while remembering that nested objects can still be shared.

<?php
$rows=[["score"=>2,"id"=>"b"],["score"=>1,"id"=>"c"],["score"=>2,"id"=>"a"]];
usort($rows,fn($a,$b)=>($a["score"]<=>$b["score"]) ?: ($a["id"]<=>$b["id"]));
echo implode(",",array_column($rows,"id")),"\n";

c,a,b

The primary comparison orders scores; only equal scores reach the identifier comparison.