PHP MySQLi mysqli_errno() - Query Error Code

mysqli_errno()

The mysqli_errno() function returns the numerical error code for the most recent function call on a specific connection.

EXAMPLE

<?php
$server = "localhost";
$username = "root";
$password = "";
$database = "mysqli_database";

$connection = mysqli_connect($server, $username, $password, $database);

// Intentionally incorrect table name to trigger an error
$table = "SELECT * FROM non_existent_table";

// NOTE: The connection to the database was successful, but the SELECT command 
// below failed because the non_existent_table does not exist in the database. 
// The mysqli_errno() function will catch this error and output its official MySQL code: 1146.
if (!mysqli_query($connection, $table)) {
    echo "Error number: " . mysqli_errno($connection);
}

mysqli_close($connection);
?>

RESULT

The result will be displayed here...

Practical use: Unlike connect_errno, this function requires the connection as a parameter. It is used to determine why an SQL command failed (e.g., code 1146 means the table does not exist). Test it at home like this:

It returns 0 if the last operation executed without errors.

Numerical codes are useful for programmatic decision-making (e.g., if the error is X, do Y).

Always use it immediately after a suspicious operation, as the next successful command resets it to 0.