uasort example

uasort

<?php

$arr = [
	[ 'foo' => 1, 'bar' => 7, 'den' => 9 ],
	[ 'foo' => 11, 'bar' => 4, 'den' => 0 ],
	[ 'foo' => 1, 'bar' => 12, 'den' => 6 ],
	[ 'foo' => 1, 'bar' => 10, 'den' => 6 ],
];

uasort( $arr, 'cmp' );
print_r( $arr );

function cmp( $a, $b ) {
	if ( $a['foo'] < $b['foo'] ) {
		return - 1;
	}

	if ( $a['foo'] === $b['foo'] ) {
		if ( $a['bar'] < $b['bar'] ) {
			return - 1;
		}

		if ( $a['bar'] === $b['bar'] ) {
			return 0;
		}

		return 1;
	}

	return 1;
}