Question

I have a code that causes the above error to show up repeatedly in my error log, how can I correct it?

public function generate_guid() {
        //you can change the length of the autogenerated guid here
        //i choose 4 because with 26 possible characters that still gives 456.976 possibilities, if you include numbers ( add 0123456789) to the possible characters you will get 1.679.616 combinations
        $length = 4;
         //charachters used for string generation
    $characters = 'abcdefghijklmnopqrstuvwxyz';
    $string = '';    
    for ($p = 0; $p < $length; $p++) {
    $string .= $characters[mt_rand(0, strlen($characters))]; <<-- this is line 92
}
return $string;
    }

Answer 1

The problem is that mt_rand(0, strlen($characters)) will generate numbers up to the strings length – but as the string offsets start with 0 the maximum offset is the length minus one. So correct would be mt_rand(0, strlen($characters) - 1).

By the way, I would recommend using a characters array generated by range('a', 'z') (so you don’t have to type it out) and getting an element using array_rand.