Question

I wrote a function which makes a random id makeid(); Just to ensure the id is unique I have a SQL statement which checks if the id already exists.

$does_id_exist = mysql_query("SELECT COUNT(*) AS count FROM signups WHERE affid='$affid'");
if(mysql_num_rows($does_id_exist) == 1) 
  { 
  #loop function and perform query again
  }
else
  {
  #insert record
  }

So I’m having trouble with looping the function. How do I loop my function makeid() and perform the $does_id_exist check to ensure that each ID is unique.

–UPDATE– Just to clarify- My code makes an id like YES@281E But before I INSERT this id into the users record. I just need to verify IF any other user already has this id. IF another user has this id that event must trigger my function to create a new id e.g. WOW!29E3 and again check the sql/query to ensure no other user has that id. Continue to loop if fails or end and INSERT if the id is available.

Answer 1

You can either just use a primary key on your database table, or something like this:

<?php
    // the id to insert
    $newId = null;

    // populate with results from a SELECT `aff_id` FROM `table`
    $currentIds = array(); 

    // prepopulate
    for( $i=0; $i<100000; $i++ )
    {
        $currentIds[] = "STRING_" + rand();
    }

    // generate at least one id
    do
    {
        $newId = "STRING_" + rand();
    }
    // while the id is taken (cached in $currentIds)
    while( in_array($newId, $currentIds) );

    // when we get here, we have an id that's not taken.
    echo $newId;    
?>

Output:

STRING_905649971 (run time 95ms);

I’d definitely not recommend running the query repeatedly. Perhaps a final check before you insert, if your traffic volume is high enough.