<?php
                      function random_strings($length_of_string)
{
  
    // String of all alphanumeric character
    $str_result = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  
    // Shuffle the $str_result and returns substring
    // of specified length
    return substr(str_shuffle($str_result), 
                       0, $length_of_string);
}
$rand=random_strings(15);
echo $rand;
?>