Question

I have a php script that makes a random token (A-Z, a-z, 0-9):

    function token($length) {

    $characters = array(
    "A","B","C","D","E","F","G","H","J","K","L","M",
    "N","P","Q","R","S","T","U","V","W","X","Y","Z",
    "a","b","c","d","e","f","g","h","i","j","k","m",
    "n","o","p","q","r","s","t","u","v","w","x","y","z",
    "1","2","3","4","5","6","7","8","9");

    //make an "empty container" or array for our keys
    $keys = array();

    //first count of $keys is empty so "1", remaining count is 1-6 = total 7 times
    while(count($keys) < $length) {
        //"0" because we use this to FIND ARRAY KEYS which has a 0 value
        //"-1" because were only concerned of number of keys which is 32 not 33
        //count($characters) = 33
        $x = mt_rand(0, count($characters)-1);
        if(!in_array($x, $keys)) {
           $keys[] = $x;
        }
    }

    foreach($keys as $key){
        $random .= $characters[$key];
    }

    return $random;

}

Works perfect, but I want to be able to check a certain database to make sure the same token has never been used before. And if it has it will instantly recreate a fresh token before outputing it.

I know I can use this script to check for a duplicate:

$check = mysqli_query($mysqli, "SELECT ".$table.".token FROM ".$table." WHERE ".$table.".token = '".$random."'");

        if(mysqli_num_rows($check) > 0){

        //ERROR: DUPLICATE TOKEN, CREATE A NEW TOKEN NOW...

        }

I just need help to add it all together, so that if a duplicate is found in the database, it will loop back and try again.

Answer 1

Put the token creation and check into a do … while loop:

do {
    $random = token(10);
    $check = mysqli_query($mysqli, "SELECT ".$table.".token FROM ".$table." WHERE ".$table.".token = '".$random."'");
} while (mysqli_num_rows($check) > 0);

By the way: You can simplify your token function as follows:

function token($length) {
    $characters = array(
        "A","B","C","D","E","F","G","H","J","K","L","M",
        "N","P","Q","R","S","T","U","V","W","X","Y","Z",
        "a","b","c","d","e","f","g","h","i","j","k","m",
        "n","o","p","q","r","s","t","u","v","w","x","y","z",
        "1","2","3","4","5","6","7","8","9");
    if ($length < 0 || $length > count($characters)) return null;
    shuffle($characters);
    return implode("", array_slice($characters, 0, $length));
}