All of the mysqli functions return false on failure, so you could easily just check for truthiness on each function and report errors.

1. Code:

<?php
/* Open a connection */
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

$mysqli->query("CREATE TABLE myCountry LIKE Country");
$mysqli->query("INSERT INTO myCountry SELECT * FROM Country");

$query = "SELECT Name, Code FROM myCountry ORDER BY Name";
if ($stmt = $mysqli->prepare($query)) {
    /* drop table */
    $mysqli->query("DROP TABLE myCountry");
    /* execute query */
    $stmt->execute();
    printf("Error: %s.\n", $stmt->error);
    /* close statement */
    $stmt->close();
}

/* close connection */
$mysqli->close();
?>

2. Definition and Usage

All of the mysqli functions return false on failure, so you could easily just check for truthiness on each function and report errors.The error / mysqli_error() function returns the last error description for the most recent function call, if any.

Syntax:

Object oriented style:

$mysqli -> error

Procedural style:

mysqli_error(connection)