Forklaring på: mt_srand((double)microtime()*1000000);

Hejsa
Jeg har fundet følgene function på nettet, nen der er en ting jeg ikke forstår.


Dette fatter jeg ikke:
---
// Seed the random number generator with the microtime stamp
// (current UNIX timestamp, but in microseconds)
mt_srand((double)microtime()*1000000);
---

En der gider at forklare hvordan ovenstående fungere og gør ?




Her er hele functionen:
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// A function to generate random alphanumeric passwords in PHP
// It expects to be passed a desired password length, but it
// none is passed the default is set to 10 (you can change this)
function generate_password($length = 10) {

    // This variable contains the list of allowable characters
    // for the password.  Note that the number 0 and the letter
    // 'O' have been removed to avoid confusion between the two.
    // The same is true of 'I' and 1
    $allowable_characters = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
   
    // We see how many characters are in the allowable list
    $ps_len = strlen($allowable_characters);

    // Seed the random number generator with the microtime stamp
    // (current UNIX timestamp, but in microseconds)
    mt_srand((double)microtime()*1000000);

    // Declare the password as a blank string.
    $pass = "";

    // Loop the number of times specified by $length
    for($i = 0; $i < $length; $i++) {
   
        // Each iteration, pick a random character from the
        // allowable string and append it to the password.
        $pass .= $allowable_characters[mt_rand(0,$ps_len-1)];
   
    } // End for

    // Retun the password we've selected
    return $pass;
}
--------------

:)