Hide mySQL error from invalid URL - mysql

Question

I have a site with 300 articles stored in a mySQL database with the URL format of www.site.com/article1.html.
Most invalid URLs redirect succesfully to the main site. For example, www.site.com/article301 redirects to www.site.com, which is what I want.
But www.site.com/article301.html does not redirect anywhere. Instead it loads a blank article template and the following error at the top of the page:
Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home//public_html/site.com/functions.php on line 26
Line 26 and down reads
if(mysql_num_rows($result)>0) {
$row=mysql_fetch_array($result);
if(ENABLE_REWRITE == 1) $path=' » '.$row['name'].''.$path;
if(ENABLE_REWRITE == 0) $path=' » '.$row['name'].''.$path;
if($row['parent']==0) $f=1;
else $id=$row['parent'];
} else {
return ' - ';
}
}
return $path;
}
Any ideas how to fix this?
Here's the full code, as requested by King Skippus
<?php
/*function get_folders_path($id) {
$f=0;
$path='';
while($f==0)
{
$result=mysql_query("SELECT name, parent FROM categories WHERE id=$id");
if(mysql_num_rows($result)>0) {
$row=mysql_fetch_array($result);
$path=' » '.$row['name'].$path;
if($row['parent']==0) $f=1;
else $id=$row['parent'];
} else {
return ' - ';
}
}
return $path;
}*/
function get_folders_path($id) {
$f=0;
$path='';
while($f==0)
{
$result=mysql_query("SELECT * FROM categories WHERE id=$id");
if($result !== FALSE && mysql_num_rows($result)>0) {
$row=mysql_fetch_array($result);
if(ENABLE_REWRITE == 1) $path=' » '.$row['name'].''.$path;
if(ENABLE_REWRITE == 0) $path=' » '.$row['name'].''.$path;
if($row['parent']==0) $f=1;
else $id=$row['parent'];
} else {
return ' - ';
}
}
return $path;
}
function get_categories_tree($id) {
static $categs = array ();
static $level=0;
$level++;
$result=mysql_query("SELECT * FROM categories WHERE parent=$id");
while($row=mysql_fetch_array($result)) {
$categs[$row['id']][0] = $row['id'];
$categs[$row['id']][1] = '/'.$row['nameurl'];
$categs[$row['id']][2] = str_repeat(' ', $level-1);
$categs[$row['id']][3] = $row['name'];
get_categories_tree($row['id']);
}
$level--;
return $categs;
}
function get_cats($id) {
$categs = array ();
$result=mysql_query("SELECT * FROM categories WHERE parent=$id");
while($row=mysql_fetch_array($result)) {
$categs[$row['id']][0] = $row['id'];
$categs[$row['id']][1] = '/'.$row['nameurl'];
// $categs[$row['id']][2] = str_repeat(' ', $level-1);
$categs[$row['id']][3] = $row['name'];
}
return $categs;
}
/*function login() {
if (!isset($_SERVER['PHP_AUTH_USER'])) {
header('WWW-Authenticate: Basic realm="My Realm"');
header('HTTP/1.0 401 Unauthorized');
return false;
} else {
$result=mysql_query("SELECT * FROM users WHERE login='{$_SERVER['PHP_AUTH_USER']}' AND password='{$_SERVER['PHP_AUTH_PW']}'");
if(mysql_num_rows($result)>0) return true;
else {
header('WWW-Authenticate: Basic realm="My Realm"');
header('HTTP/1.0 401 Unauthorized');
return false;
}
}
}*/
function login() {
if (!isset($_SESSION['AUTH_USER']) || !isset($_SESSION['AUTH_PASS'])) return false;
else {
$result=mysql_query("SELECT * FROM users WHERE login='{$_SESSION['AUTH_USER']}' AND password='{$_SESSION['AUTH_PASS']}'");
if(mysql_num_rows($result)>0) return true;
else return false;
}
}
function get_categories($id) {
static $categs = array ("0" => "[Top]");
static $level=0;
$level++;
$result=mysql_query("SELECT * FROM categories WHERE parent=$id");
while($row=mysql_fetch_array($result)) {
$categs[$row['id']] = str_repeat('| ', $level-1).'|___'.$row['name'];
get_categories($row['id']);
}
$level--;
return $categs;
}
function get_parent_name($id) {
if($id!=0) {
$result=mysql_query("SELECT name FROM categories WHERE id=$id");
if(mysql_num_rows($result)>0) {
$row=mysql_fetch_array($result);
return $row['name'];
}
else return '-';
}
else return 'Top';
}
function getcatname($id, $table)
{
$r=mysql_query("SELECT title FROM $table WHERE id='$id'");
if(mysql_num_rows($r)>0) {
$row=mysql_fetch_array($r);
return $row['title'];
}
else
return "-";
}
?>

Answer 1

Probably your query failed, and you have no error handling. Your basic bare-bones query sequence should be:
$result = mysql_query($sql) or die(mysql_error());
^^^^^^^^^^^^^^^^^^^^^^
If you assume the query succeeded and blindly use $result later, you tend to get the type of errors you do, as mysql_query will return a boolean FALSE when something goes boom. That FALSE is not a valid statement handle, so the subsequent num_rows/fetch calls will also go boom.
Never assume a query has succeeded. Even if your sql syntax is 100% perfect, there's far too many other reasons for failure to NOT check.

Answer 2

Try replacing
if(mysql_num_rows($result)>0) {
with
if($result === FALSE) {
header('Location: http://www.example.com/');
}
else if (mysql_num_rows($result)>0) {
// Query was valid, but no rows returned. Take appropriate action.
}
EDIT
For troubleshooting purposes, what does it display if you change the function to this instead? Please be aware that this will intentionally break your site, but it will provide data that is useful for troubleshooting.
function get_folders_path($id) {
$f=0;
$path='';
while($f==0)
{
$result=mysql_query("SELECT * FROM categories WHERE id=$id");
die(sprintf("Value of id: %s, MySQL Error: %s",
var_dump($id, true), var_dump(mysql_error($result), true)));
// Leave the rest of your function as-is, just insert the line above.