PHP Loop/Go Back

Question

Let's say I have given a user an access code. I have generated the code in php and would like to insert this random access code into the database, however it has to be unique to that user. So, when I have created the code and it checks to see if that code already exists in the database, if it returns true (as in, it is already existing), I want the script to "go back" or "loop" until it generates one that doesn't already exist.

I know how to generate the code, and how to insert into the mysql database. My question is simply, how would I go about writing the "loop" portion?

Perhaps you should look into a recursive function. http://stackoverflow.com/questions/2648968/what-is-a-recursive-function-in-php — CD Brian, May 05 '15 at 02:55
Can you not simply have a loop do this? While in database is true? — Jonathan Holland, May 05 '15 at 02:56
why not just generate unique codes right off the bat? many ways to do this, rather than regenerating all the time and be a waste of time, *at best*. All this using a UNIQUE constraint. — Funk Forty Niner, May 05 '15 at 02:57

score 1 · Answer 1 · answered May 05 '15 at 02:59

Why not generate something unique with a quality method instead of making a code, and checking if its already in the database?

Do something like,

hash($username)

So, aslong as the "username" is unique, the code will be unique as well.

P.S : hash, I just mentioned in the code, can be any hashing algorithm. Md5(not that recommend),Sha1 or whatever.

Devon · Answer 2 · 2015-05-05T03:16:08.457

0

You can end a loop with break. So loop, then when the variable is false -- meaning you have a unique code, stop the loop with break.

while {
   ...
   if ($variable === false) {
      break;
   }
}

Or even:

$variable = true;
while ($variable) {
   ...
   $variable =  isItInTheDatabase();
}

Which would stop the loop once $variable is false, null, or 0.

edited May 05 '15 at 03:16

answered May 05 '15 at 02:58

Devon

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score 0 · Answer 3 · answered May 05 '15 at 02:59

0

do {
$code = generate_a_random_string();
} while(mysql_num_rows(mysql_query("select * from table where code = '".mysql_real_escape_string($code)."'")))

// Insert the code

answered May 05 '15 at 02:59

Alex83690

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score 0 · Answer 4 · answered May 05 '15 at 03:02

0

Its very simple generate really a unique that can't be repeated by code generator, you can use timestamp and extra character.

answered May 05 '15 at 03:02

Varun Naharia

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PHP Loop/Go Back

4 Answers4