Code to create Dynamic Random Number using PHP

Here is the Code:

function generateRandomNo ($length)

{

$output = "";

$options = "0123456789abcdefghijklmnopqrstuvwxyz";

$count = 0;

while ($count < $length)

{

$char = substr($options, mt_rand(0, strlen($options)-1), 1);

if (!strstr($output, $char)) {

$output .= $char;

$count++;

}

}

return $output;

}