note 92223 deleted from function.usort by danbrown

Note Submitter: Peter Kionga-Kamau ---- As of PHP 4.1.0: "A new sort algorithm was introduced. The cmp_function doesn't keep the original order for elements comparing as equal." So... in case you want to sort a 2-d array by multiple keys in the sub-arrays, multiple calls to the usort() function *do not* work. usort() almost assuredly mixes up the element order from prior sorts in cases where elements evaluate as equal in the previous call. Below is a function that will maintain this order: function SUBKEY_SORT(&$a,$k,$d=false) { // sorts a 2-d array by key $k, *maintaining orignial order* of equal items ($d=sort descending) // *DOES NOT maintain associations!* To maintain associations, see SUBKEY_ASORT() // // © 2009 Peter Mugane Kionga-Kamau (http://www.mugane.com) // // e.g. to sort a 2-d array of user data ($people) by last name then first name: // SUBKEY_SORT($people,"fname"); // SUBKEY_SORT($people,"lname"); // most relevant key used in the final call. // // Free for unrestricted use, as long as this notice remains intact. // $u = array(); // stores all unique items: foreach($a as $x=>$y) $u[(string)$y[$k]][$x]=true; // pass 1: extract unique entries in orignial order $d?krsort($u):ksort($u); $t = array(); // stores sorted array foreach($u as $p=>$q) foreach($q as $w=>$z) $t[] = $a[$w]; // pass 2: populate sorted array return $a=$t; }