My failed attempt:
$post_id = preg_match("/^[0-9]+$/", $_POST['post_id']);
I tried to be a user who changed the post id for example: post_id="43223646", but when the data is entered in mysql, they are transformed into the number 1, how to make it work correctly?
The preg_match of PHP returns 1 if the expression matched, 0 if it did not match and false if an error occurred.
In your case, you are returning 1 because you are combining.
But since you want the value itself, you should use the third parameter:
matches
If matches is provided, it will be populated with the search results.
Do this:
preg_match("/^[0-9]+$/", $_POST['post_id'], $matches);
$post_id = $matches[0];