PHP MySQLi mysqli_get_warnings() - Warning Diagnostics

mysqli_get_warnings()

The mysqli_get_warnings() function returns an object containing warnings that occurred during the execution of the last query. This is crucial for detecting issues such as incorrect data types or truncated text that do not stop the script execution.

EXAMPLE

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

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

// Intentionally insert an incorrect date format to trigger a server warning
mysqli_query($connection, "INSERT INTO mysqli_table (fruit, vegetable, date) VALUES ('Pear', 'Lettuce', 'wrong_date')");

// Check if any warnings exist
if (mysqli_warning_count($connection)) {
    // NOTE: The mysqli_get_warnings() function returns an object containing the warning.
    // Since a single query can trigger multiple warnings at once, we use a 
    // do...while loop and the ->next() method to iterate through subsequent 
    // warnings until there are no more left.
    $warning = mysqli_get_warnings($connection);
    do {
        printf("Warning (%d): %s<br>", $warning->errno, $warning->message);
    } while ($warning->next());
} else {
    echo "No warnings detected.";
}

mysqli_close($connection);
?>

RESULT

The result will be displayed here...

Practical use: If a query returns a warning (e.g., when dividing by zero or converting strings), you can use this function to output the error code and message. Look at the example:

It returns an object of type mysqli_warning or FALSE if there are no warnings.

It provides access to properties: message, sqlstate, and errno.

It helps maintain high data quality in the database.