$lenght = 13;
$count = 5;
<?php
function randomString($count = 5, $length = 15) {
$chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
$charsLen = strlen($chars);
$res = [];
for($i = 0; $i < $count; $i++) {
$tmp = '';
for ($j = 0; $j < $length; $j++) {
$tmp .= $chars[rand(0, $charsLen - 1)];
}
$res[] = $tmp;
}
return $res;
}
var_dump(randomString());