Trier un tableau multidimensionnel selon 2 colonnes

SELECT * FROM tab ORDER BY longueur DESC AND largeur DESC

A nice way to do sorting of a key on a multi-dimensional array without having to know what keys you have in the array first:

<?php
$people = array(
array("name"=>"Bob","age"=>8,"colour"=>"red"),
array("name"=>"Greg","age"=>12,"colour"=>"blue"),
array("name"=>"Andy","age"=>5,"colour"=>"purple"));

var_dump($people);

$sortArray = array();

foreach($people as $person){
    foreach($person as $key=>$value){
        if(!isset($sortArray[$key])){
            $sortArray[$key] = array();
        }
        $sortArray[$key][] = $value;
    }
}

$orderby = "name"; //change this to whatever key you want from the array

array_multisort($sortArray[$orderby],SORT_DESC,$people);

var_dump($people);
?>

Output from first var_dump:

[0]=>
  array(3) {
    ["name"]=>
    string(3) "Bob"
    ["age"]=>
    int(8)
    ["colour"]=>
    string(3) "red"
  }
  [1]=>
  array(3) {
    ["name"]=>

    string(4) "Greg"
    ["age"]=>
    int(12)
    ["colour"]=>
    string(4) "blue"
  }
  [2]=>
  array(3) {
    ["name"]=>
    string(4) "Andy"
    ["age"]=>
    int(5)
    ["colour"]=>

    string(6) "purple"
  }
}

Output from 2nd var_dump:

array(3) {
  [0]=>
  array(3) {
    ["name"]=>
    string(4) "Greg"
    ["age"]=>
    int(12)
    ["colour"]=>
    string(4) "blue"
  }
  [1]=>
  array(3) {
    ["name"]=>

    string(3) "Bob"
    ["age"]=>
    int(8)
    ["colour"]=>
    string(3) "red"
  }
  [2]=>
  array(3) {
    ["name"]=>
    string(4) "Andy"
    ["age"]=>
    int(5)
    ["colour"]=>

    string(6) "purple"
  }

There's no checking on whether your array keys exist, or the array data you are searching on is actually there, but easy enough to add.