PHP Recursive function issue

Question

I am having trouble with the getNext() function...

If isTaken() == true, it does update last, but I'm not sure it is invoking the getNext() function as the function never returns $next.

If isTaken() == false, $next is returned.

Any ideas?

function isTaken ($id){
  $sql = "SELECT asset_no FROM tb_asset WHERE asset_no='" . $id . "'";
  $result = mysql_query($sql) or die(mysql_Error());
  if (mysql_num_rows($result)) return true;
  else return false;  
  mysql_free_result($result);
}


function getNext(){
  $sql = "SELECT last FROM app_asset";
  $result = mysql_query($sql) or die (mysql_error());
  $last = mysql_fetch_array($result);
  mysql_free_result($result);

  $next = ++$last['last'];

  if (isTaken($next)){
    $sql = "UPDATE app_asset SET last='" . $next . "'";
    mysql_query($sql) or die (mysql_error());
    getNext();
  } else {  
    return $next;
  }
}

Please don't use mysql_query. It's deprecated and insecure. — MattDiamant
– MattDiamant, Commented Nov 16, 2013 at 21:19
@MattDiamant what do you suggest...mysqli? Or are you refering to the way mysql_query is used? — Mike
– Mike, Commented Nov 16, 2013 at 21:36
@Mike PDO or MySQLi are the usual replacements. See this tutorial or this page in the manual for more information — kero
– kero, Commented Nov 16, 2013 at 21:42

kero · Accepted Answer · 2013-11-16 21:29:28Z

1

As Sable Foste pointed out, you will always need a return statement. In your case however, it looks like your code needs to be modified to

if (isTaken($next)){
    //code
    return getNext();
} else
    return $next;

So the function will stop the recursion and return once isTaken($next) is false

answered Nov 16, 2013 at 21:29

kero

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Comments

Sablefoste · Accepted Answer · 2013-11-16 21:19:02Z

0

You need to pass the variable back to the function:

  if (isTaken($next)){
    $sql = "UPDATE app_asset SET last='" . $next . "'";
    mysql_query($sql) or die (mysql_error());
    getNext();
    return $next; // this line added.
  } else {  
    return $next;
  }

answered Nov 16, 2013 at 21:19

Sablefoste

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3 Comments

kero Over a year ago

Actually this could be simplified to if (..) {...} return $next; (since both cases of the if have the same return statement), but you made your point clear.

Mike Over a year ago

That does not work. I can only return $next when isTaken() == false. In your answer $next is returned before the function is finished and returns a result that is taken.

Sablefoste Over a year ago

@Mike, because this is a recursive array, you need to return something on every recursion. Otherwise, you will only get the final result if no recursion occurs. If not $next, then use a different value to return.

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