PHP MySQLi mysqli_warning_count()

mysqli_warning_count()

The mysqli_warning_count() function returns the number of warnings that occurred during the execution of the last SQL query. Warnings differ from errors as they do not stop execution but merely warn about irregularities.

EXAMPLE

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

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

if (mysqli_connect_errno()) {
    echo "Connection failed: " . mysqli_connect_error();
    exit();
}

// Attempt to insert a string longer than 5 characters into a field limited to VARCHAR(5)
$sql = "INSERT INTO test (id, info) VALUES (1, 'TooLongString')";

mysqli_query($connection, $sql);

// Check the number of silent server warnings
// NOTE: Some commands appear to execute successfully, but MySQL generates a warning 
// in the background (e.g., if it truncates text that is too long or converts an invalid date). 
// This function returns the exact number of such warnings, allowing you to catch hidden errors in time.
$warning_count = mysqli_warning_count($connection);

echo "Number of warnings in the last query: " . $warning_count;

if ($warning_count > 0) {
    echo "<br>Tip: Check the length or data type of the data you are inserting.";
}

mysqli_close($connection);
?>

RESULT

The result will be displayed here...

Practical use: Warnings often appear if you try to insert text that is too long into a field with a limited number of characters, or if you insert an incorrect data type (e.g., text instead of a number). MySQL will attempt to adjust the data but will issue a warning about it.

It returns an integer (the number of warnings).

Warnings are not critical errors, but they can lead to data loss (e.g., a truncated string).

To view warnings in more detail, use the SQL command SHOW WARNINGS.