How to Retrieve MySQL Error Message for Complex Queries

In PHP, executing long MySQL queries that rely on user input can occasionally result in errors. However, obtaining a detailed error message to identify the root cause of the failure can be challenging.

Implementing Error Message Display

To display error messages, modify your code as follows:

$result = mysqli_query($this->db_link, $query) or die(mysqli_error($this->db_link));

Handling Query Execution Errors

The code above utilizes the mysqli_query() function and the or die() statement to handle query execution errors. If the query fails, PHP will terminate the script and print the error message returned by the mysqli_error() function.

Retrieving Error Code

In addition to the error message, you can also retrieve the error code by adding the following line to your code:

echo mysqli_errno($this->db_link);

This will output the numerical error code associated with the query failure.

Referencing Documentation

For further information on handling database errors in PHP, refer to the following documentation:

• [mysqli_query()](https://www.php.net/manual/en/function.mysqli-query.php)
• [mysqli_error()](https://www.php.net/manual/en/function.mysqli-error.php)
• [mysqli_errno()](https://www.php.net/manual/en/function.mysqli-errno.php)