Another problem with mySQL_num_rows

[royalbi]

I am a newbie in PHP and mySQL. I got stuck with a mySQL function and could not figure out the problem. I would appreciate very much if any expert in this forum could help.

I learned and reused a function get_category_name($catid) from page 554, listing 25.7 of the book PHP and mySQL - web development. The code is as following:

function get_category_name($catid)
{
$conn = db_connect();
$query = " select catname
from categories
where catid = $catid";
$result = @($query);
if (!$result)
return false;
$num_cats = @mysql_num_rows($result);
if ($num_cats ==0)
return false;
$result = mysql_result($result, 0, "catname";
return $result;
}

I dont know why mysql_num_rows($result) could not get any value while mysql_query($query) had returned some values in the $result. I got stuck where $num_cats = @mysql_num_rows($result) return false.

Thanks again for help.

[RedDragon]

your code is missing some brain 🙂

you say

if (!$result)
return false;
$num_cats = @mysql_num_rows($result);

if there is no result you try to count the rows of it...
so it will alway be FALSE

function get_category_name($catid)
{
$conn = db_connect();
$query = " select catname
from categories
where catid = $catid";
$result = @($query);
if (!$result)
return false;
$num_cats = @mysql_num_rows($result);
if ($num_cats ==0)
return false;
$result = mysql_result($result, 0, "catname";
return $result;
}

[royalbi]

Thanks for your response.

However as i expressed from the beginning, i am a newbie and i REUSED the code frorm a book PHP and MySQL Web Development written by Luke Welling and Laura Thomson.

The source code accompanied with the book works perfectly fine itself in the sample project, which is a online bookshop. The code i posted previouly was the original code of a function without changing any thing. I only tried to use this code in my database which was created with the same database structure as explained in the book.

I hope there is someone in this forum could help rectified the problem.

Thanks.

[RedDragon]

this should do it:

function get_category_name($catid) {
$conn = db_connect(); 
$query = "SELECT catname FROM categories WHERE catid = $catid";
$result = mysql_query($query) or die(mysql_error());
$num_cats = mysql_num_rows($result); 
if($num_cats==0) {
return FALSE;
} else {
return $num_cats;
}

[royalbi]

Thank you again RedDragon.

The mistake was not due to that code. It was some silly missing out in my database. Got it corrected already. Thanks for your posting.😉