note 105265 added to function.array-rand

Looks like this function has a strange randomness. If you take any number of elements in an array which has 40..100 elements, the 31st one is always by far the less occuring (by about 10% less than others). I tried this piece of code at home (PHP Version 5.3.2-1ubuntu4.9) and on my server (PHP Version 5.2.17), unfortunately i haven't any server with the last version here : <?php $valeurs = range(1, 40); $proba = array_fill(1, 40, 0); for ($i = 0; $i < 10000; ++$i) { $tirage_tab = array_rand($valeurs, 10); foreach($tirage_tab as $key => $value) { $proba[$valeurs[$value]]++; } } asort($proba); echo "Proba : <br/>\n"; foreach($proba as $key => $value) { echo "$key : $value<br/>\n"; } ?> In every try, the number of occurrences change a bit but the 31 is always far less (around 2200) than the others (2400-2600). I tried with 50 and 100 elements, no change. I tried with more or less elements to pick (second parameter to array_rand), same result. If you pick only one element it's even worse : 31 has half the result of the others. For this particular case, i recommend shuffling the array and taking the nth first elements, in this test it's 60% faster and the statistics are ok. ---- Server IP: 69.147.83.197 Probable Submitter: 88.165.96.36 ---- Manual Page -- http://www.php.net/manual/en/function.array-rand.php Edit -- https://master.php.net/note/edit/105265 Del: integrated -- https://master.php.net/note/delete/105265/integrated Del: useless -- https://master.php.net/note/delete/105265/useless Del: bad code -- https://master.php.net/note/delete/105265/bad+code Del: spam -- https://master.php.net/note/delete/105265/spam Del: non-english -- https://master.php.net/note/delete/105265/non-english Del: in docs -- https://master.php.net/note/delete/105265/in+docs Del: other reasons-- https://master.php.net/note/delete/105265 Reject -- https://master.php.net/note/reject/105265 Search -- https://master.php.net/manage/user-notes.php