There could be several layers where issues may arise: the database connection, the query itself, or the data being sent.
It's also important to note that not filtering for " and ' marks can lead to problems, and not ensuring that the id is a number may cause SQL failures.
To troubleshoot, consider adding diagnostics to your code to check what MySQL reports as the error, providing insight on how to resolve it.
While it is generally suggested to use the mysqli extension instead of mysql extension, below is sample code using the current extension you are utilizing.
I hope this guidance proves helpful!
<?php
if ( isset($_GET['deletecat'])) {
#dbh -> represents the database resource.
$dbh = mysql_connect()
#mysql_connect returns false if unsuccessful. Capture the error and display it.
if (!$dbh) {
die("Could not connect to the database server: ".mysql_error()."\n");
#if using mysqli, utilize mysql_connect_error() instead
}
#Use an escape function to prevent injection attacks.
$id_to_delete = mysql_real_escape_string($_GET['deletecat'],$dbh);
#Ensure $id_to_delete is treated as a number in your SQL statement. I have corrected it below.
$sql = "DELETE FROM `category` WHERE `Category_id` = '$id_to_delete' LIMIT 1");
#Check if the query was successful.
$result = mysql_query($sql,$dbh);
#In case of failure, catch the error and display relevant information in a user-friendly manner.
if (!$result) {
$error=mysql_error($dbh);
die ("Error: Could not delete '"
.htmlentities(print_r($_GET['deletecat'],true)).". Error: $error\n"
);
}
#If no errors were encountered, proceed with redirecting.
header('location: category.php');
exit();
}
?>
[1]: For cautionary notes, refer to http://php.net/manual/en/function.mysql-connect.php