Bug #17307 Updated: sorting using usort() does not produce correct result anymore

ID: 17307 Updated by: fcartegnie@nordnet.fr Reported By: fcartegnie@nordnet.fr Status: Feedback Bug Type: Arrays related Operating System: Linux PHP Version: 4.2.1 New Comment: <?php /* let's define some array elements For example, 3 products (A,B,C) with different price (livre) */ $elt["nom"]="A"; $elt["livre"]=10; $elt["quantite"]=1; $ar[]=$elt; $elt["nom"]="A"; $elt["livre"]=9; $elt["quantite"]=1; $ar[]=$elt; $elt["nom"]="A"; $elt["livre"]=7; $elt["quantite"]=1; $ar[]=$elt; $elt["nom"]="A"; $elt["livre"]=11; $elt["quantite"]=1; $ar[]=$elt; $elt["nom"]="A"; $elt["livre"]=101; $elt["quantite"]=1; $ar[]=$elt; $elt["nom"]="B"; $elt["livre"]=104; $elt["quantite"]=1; $ar[]=$elt; $elt["nom"]="C"; $elt["livre"]=101; $elt["quantite"]=1; $ar[]=$elt; /* Our sort function only swap 2 values if the name is the same and the first price is higher than second As we give a 'nom' field sorted alphabetically array, we might get the result : A7 A9 A10 A11 A101 B104 C101 Which is the result in php 4.0.6 But the result un php 4.2.1 is : C101 B104 A7 A9 A10 A11 A101 */ function sort_function($a, $b) { if ((($a["livre"]/$a["quantite"]) == ($b["livre"]/$b["quantite"])) || $a["nom"] != $b["nom"]) return 0; return (($a["livre"]/$a["quantite"]) < ($b["livre"]/$b["quantite"])) ? -1 : 1; } /* This is a 2nd function, which always returns that elements are equal. So it might not change the array... If you try this alternate function, you'll see that the array is modified to : B104 C101 A101 A11 A9 A7 A10 ??????! really strange behaviour */ function sort_function_void($a, $b) { return 0; } echo "<HTML><PRE>UnSorted:\n"; for ($i=0;$i<sizeof($ar);$i++) echo $ar[$i]["nom"].$ar[$i]["livre"]."\n"; usort($ar, sort_function); //usort($ar, sort_function_void); echo "Sorted:\n"; for ($i=0;$i<sizeof($ar);$i++) echo $ar[$i]["nom"].$ar[$i]["livre"]."\n"; ?> Previous Comments: ------------------------------------------------------------------------ [2002-05-22 08:45:20] fcartegnie@nordnet.fr Huh ... Related to Bug #17257 ;) ------------------------------------------------------------------------ [2002-05-22 08:44:49] fcartegnie@nordnet.fr Related to Bug #17307 ------------------------------------------------------------------------ [2002-05-18 08:49:39] derick@php.net Please prive a short self containing script (which runs right away after copy&paste). Derick ------------------------------------------------------------------------ [2002-05-18 08:36:08] fcartegnie@nordnet.fr I used to make sorts with usort and calling the function below. This was working on the last versions but not anymore on the 4.2.1 :/ which outputs strange result. function sort_function($a, $b) { if ((($a["livre"]/$a["quantite"]) == ($b["livre"]/$b["quantite"])) || $a["nom"] != $b["nom"]) return 0; return (($a["livre"]/$a["quantite"]) < ($b["livre"]/$b["quantite"])) ? -1 : 1; } ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=17307&edit=1