警告mysql_num_rows（）：提供的参数不是有效的MySQL结果

Question

Why i have this error and how to fix this, I've double checked everything and all is okay

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/sharinga/public_html/ccccc.com/app/like/like.php on line 15
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'like WHERE postID='81' AND userIP='2x2.2x0.x5.xxx'' at line 1

Here is sql

$ip_sql = mysql_query("SELECT userIP FROM like WHERE postID='$id' AND userIP='$ip'");
$count = mysql_num_rows($ip_sql) or die(mysql_error());
if($count==0)
{...

Answer 1

LIKE is a reserved word - escape it

$ip_sql = mysql_query("SELECT userIP FROM `like` WHERE postID='$id' AND userIP='$ip'");