When should persistent database connections be used in PHP applications?

Persistent database connections should be used in PHP applications when there is a need to improve performance by reducing the overhead of establishing a new connection for each request. By using persistent connections, the connection to the database server is not closed when the execution of the script ends, allowing subsequent requests to reuse the same connection. This can lead to faster response times and better scalability for applications with high traffic.

// Establish a persistent database connection using mysqli
$mysqli = new mysqli('localhost', 'username', 'password', 'database', null, null, MYSQLI_CLIENT_COMPRESS | MYSQLI_CLIENT_SSL_DONT_VERIFY_SERVER_CERT);
if ($mysqli->connect_error) {
    die('Connect Error (' . $mysqli->connect_errno . ') ' . $mysqli->connect_error);
}

// Use the $mysqli object to query the database
$result = $mysqli->query("SELECT * FROM table_name");
if ($result) {
    while ($row = $result->fetch_assoc()) {
        // Process the data
    }
    $result->free();
}

// Close the connection when done
$mysqli->close();