= mysql_num_rows

[otuatail]

$sql = "SELECT current FROM LIBusersX WHERE UserKey = '$Key' AND K_Type = $type AND current > 0 ";
	// echo $sql . "<br>";
	$query = mysql_query ($sql) or die ("E112-100A");
	$total = mysql_num_rows($query) or die ("E112-101A");

Hi

I have a website with a few users. I set up a system so that some users (as a trial) can only log on a fixed number of times. I have a field called current that counts down to zero. However when it reaches zero I get my error E112-101A

 

Why do I get an error? Surely I should just get $total = 0

 

 

 

[Barand]

See what mysql_error() has to say about it.

[Frank_b]

$total = mysql_num_rows($query) or die ("E112-101A");

that is unlogic. The keyword or takes a role in a logic expression. Think about 

if(mysql_num_rows($query) or die ("E112-101A"))
    ...

if the first part of the expression (before the or) gives a TRUE than the expression will stop. But if the first part gives FALSE the expression will continue with the second part after the as which does stop your script with die(). For the case that you might not know it, FALSE equals to 0 (zero) and all other values equals to TRUE.

 

in more helpfull words i could say that mysql_num_rows() and the combination 'or die()' is a very bad combination.You should alway check php.net for what values could be returned by the function you use, in this case the mysql_num_rows() function. Just take a look under the "Return Values" chapter here: http://www.php.net/manual/en/function.mysql-num-rows.php. you will learn that any value from of zero can be returned or FALSE on failures. 

 

Now comes a little bit hard to understand part of PHP. PHP can distinguish a FALSE from a 0 but you should use a special === or !== operator.

$rows = mysql_num_rows($query);
if($rows === FALSE)
   die('E112-101A');