String Uninitialized string offset -PHP

Question

When Im running the next code:

function RandomLink()
        {
        $characters = "0123456789abcdefghijklmnopqrstuvwxyz";
        $string = "";
        for($x = 0; $x< 30; $x++)           
            {
              $string .= $characters[(mt_rand(0, strlen($characters)))]; // Random char
            }

        return "$string.php";
        }

I get an error which says: Uninitialized string offset .What it mean's and how can i fix it? I just dont want programming like a robot,I want understands behind the error may someone explain me too? Thank you very much !

Try replacing strlen($characters) with strlen($characters) - 1 — StephenTG
– StephenTG, Commented Aug 2, 2013 at 15:23
Worked thanks ! It was because the string length was too long ? — Sababoni
– Sababoni, Commented Aug 2, 2013 at 15:24
Yeah. Since the index starts at 0, the last index in the string is actually 1 less than the length — StephenTG
– StephenTG, Commented Aug 2, 2013 at 15:25
It's because the string is 0-indexed to 35 and your mt_rand goes from 0 to 36. — Maxime Lorant
– Maxime Lorant, Commented Aug 2, 2013 at 15:25

Kirk Backus · Accepted Answer · 2013-08-02 15:27:19Z

2

Your problem is that mt_rand parameter max is inclusive. So strlen($characters) should be strlen($characters)-1 since there is no character at the index equivalent of the length of the string.

$string .= $characters[(mt_rand(0, strlen($characters)-1))];

If your string was length of 2 like "ab" then mt_rand(0, 2) would return values 0, 1, and 2, which is a, b, and JUST ONE TOO FAR.

answered Aug 2, 2013 at 15:27

Kirk Backus

4,8764 gold badges34 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Jason McCreary · Accepted Answer · 2013-08-02 15:24:25Z

0

As noted in the comments, the offset you provided to mt_rand() is beyond $characters length. Update the strlen($characters) - 1.

Also, you've recreated - str_shuffle():

Consider refactoring to:

function RandomLink() {
  $characters = "0123456789abcdefghijklmnopqrstuvwxyz";
  $hash = str_shuffle($characters);
  return substr($hash, 0, 30) . '.php';
}

answered Aug 2, 2013 at 15:24

Jason McCreary

73.3k23 gold badges140 silver badges177 bronze badges

Collectives™ on Stack Overflow

String Uninitialized string offset -PHP

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related