if mysql_query() fails, what to do?

Question

Sometimes so happens that mysql_query() fails to INSERT data and I am unaware of it. So, the question is how do I know when it happens?

Answer 1

Quoting the documentation page of mysql_query :

For SELECT, SHOW, DESCRIBE, EXPLAIN and other statements returning resultset, mysql_query() returns a resource on success, or FALSE on error.

For other type of SQL statements, INSERT, UPDATE, DELETE, DROP, etc, mysql_query() returns TRUE on success or FALSE on error.

So, to detect whether there's been an error or not, you have to test the return value of your call to mysql_query :

$result = mysql_query('...');
if ($result === false) {
    // And error has occured while executing
    // the SQL query
}

Then, what can you do ?

• Well, first, you can log the error to a file, that you can analyse later
  • For than, you can use mysql_error and mysql_errno.
• And you can display a nice error message the user
  • i.e. some kind of "oops, an error occured page".

Remember, though : the user doesn't need to know (and will not understand) the technical error message -- so don't display it.