Controlled Random String, Password Generator

This function lets you get controlled random strings, numbers or passwords.

function VISION_TO_RANDOM
(
//autor: Femi Hasani [www.vision.to]
$length=7, //string length
$uselower=1, //use lowercase letters
$useupper=1, // use uppercase letters
$usespecial=1, //use special characters
$usenumbers=1, //use numbers
$prefix=''
)
{

    $key = $prefix;
// Seed random number generator
    srand((double)microtime() * rand(1000000, 9999999));
    $charset = "";
    if ($uselower == 1) $charset .= "abcdefghijkmnopqrstuvwxyz";
    if ($useupper == 1) $charset .= "ABCDEFGHIJKLMNPQRSTUVWXYZ";
    if ($usenumbers == 1) $charset .= "0123456789";
    if ($usespecial == 1) $charset .= "~#$%^*()_+-={}|][";
    while ($length > 0) {
        $key .= $charset[rand(0, strlen($charset)-1)];
        $length--;
    }
    return $key;
}