[PHP]Making something randomly fail/succeed.

I need to know how to make something randomly fail.
E.x someone sends a form to roll a dice, with 75% luck, how to make that 75% real?
I tried doin' it with rand(); but I didnt make it x[

Elite.

PHP Code:

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<?php
// Create a rand() for 100 possibilities
$rand = rand(1,100);
// A 75% success rate would be either ">= 25" OR "<= 75"
if($rand >= 25)
{
    // If its within the given amount, show the dice...
    // For this example, I chose the 75% chance to roll a 6
    echo '<img src="6.jpg">';
}
// Else... Failed and it will choose between the other sides of the dice
else
{
    // 6 had the 75% and failed
    // So the remaining sides on the dice are 1 - 5
    $card_rand = rand(1,5);
    // Echo the image
    echo '<img src="' . $card_rand . '.jpg">';
}
// Final Notes!
// This is assuming your using images and the images are 
// 1.jpg, 2.jpg, upto 6.jpg
?>

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Thanks, I just forgot the method I did it =p

Thanks for the help,

Elite.

you should use the mt_rand() function istead, it's four times faster ;P