why does this function not work?

[wreikun]

hey everyone. im in the process of learning MySQL with PHP from a book, and one of the example scripts doesnt seem to be working. The problem lies in the built-in function 'mysql_num_rows()'. part of the example script is listed below with the 'mysql_num_row()' function. Can anyone let me know what I'm getting wrong here? when the php script is run, i get the following displayed in my browser:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource

this is an excerpt of the php script:

mysql_select_db("books"
$query = "select * from books where ".$searchtype." like '%".searchterm."%'";
$result = mysql_query($query);
$num_results = mysql_num_rows($result);

echo &quot;<p>Number of books found: &quot;.$num_results.&quot;</p>&quot;;

for ($i=0; $i<$num_results; $i++){
$row = mysql_fetch_array($result);
echo &quot;<p><strong>&quot;.($i+1).&quot;. Title: &quot;;
echo htmlspecialchars(stripslashes($row[&quot;title&quot;]));
echo &quot;</strong><br>Author: &quot;;
echo htmlspecialchars(stripslashes($row[&quot;author&quot;]));
echo &quot;<br>ISBN: &quot;;
echo htmlspecialchars(stripslashes($row[&quot;isbn&quot;]));
echo &quot;<br>Price: &quot;;
echo htmlspecialchars(stripslashes($row[&quot;price&quot;]));
echo &quot;</p>&quot;;
}

thanks,
REI

 

[danielhozac]

Try changing

$query = "select * from books where ".$searchtype." like '%".searchterm."%'";
$result = mysql_query($query);
$num_results = mysql_num_rows($result);

to

$query = "select * from books where ".$searchtype." like '%".$searchterm."%'";
$result = mysql_query($query) or die("Couldn't query");
$num_results = mysql_num_rows($result);

This would print an error if the querying doesn't work. //Daniel

 

[wreikun]

Hello. Thanks for the tip on how to check if the querying works or not. I added the 'die(&quot;Couldnt query&quot' and tried viewing the php page through my browser and the words &quot;Couldnt query&quot; were displayed which obviously means that the querying doesnt work.

Now my question is: what are some possible reasons on why the mysql_query() function isnt working?

Any help is appreciated!

Thanks in advance,
REI

 

[danielhozac]

Try printing the contents of the query. Does it look right? Could you post it here?
mysql_query returns false if it fails, meaning that the query returned an error from the database backend. //Daniel

 

[wreikun]

Thanks for the reply. Ive been trying to figure this out for a lil while now, and Ive been able to narrow it down to this line:

mysql_connect(&quot;localhost&quot;

I wasnt able to connect to mysql server, thus the functions mysql_query(), and mysql_num_rows() didnt work.

I changed that line to the following:
mysql_connect(&quot;localhost&quot;, &quot;root&quot;

and it worked as expected.

Now, I gotta try to figure out how this whole username thing works in mysql.

thanks for the help daniel.

--REI