PHP Decode

<?php 
 
if( isset( $_GET[ 'Submit' ] ) ) { 
	// Check Anti-CSRF token 
	checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' ); 
	$exists = false; 
 
	// Get input 
	$id = $_GET[ 'id' ]; 
 
	// Was a number entered? 
	if(is_numeric( $id )) { 
		$id = intval ($id); 
		switch ($_DVWA['SQLI_DB']) { 
			case MYSQL: 
				// Check the database 
				$data = $db->prepare( 'SELECT first_name, last_name FROM users WHERE user_id = (:id) LIMIT 1;' ); 
				$data->bindParam( ':id', $id, PDO::PARAM_INT ); 
				$data->execute(); 
 
				$exists = $data->rowCount(); 
				break; 
			case SQLITE: 
				global $sqlite_db_connection; 
 
				$stmt = $sqlite_db_connection->prepare('SELECT COUNT(first_name) AS numrows FROM users WHERE user_id = :id LIMIT 1;' ); 
				$stmt->bindValue(':id',$id,SQLITE3_INTEGER); 
				$result = $stmt->execute(); 
				$result->finalize(); 
				if ($result !== false) { 
					// There is no way to get the number of rows returned 
					// This checks the number of columns (not rows) just 
					// as a precaution, but it won't stop someone dumping 
					// multiple rows and viewing them one at a time. 
 
					$num_columns = $result->numColumns(); 
					if ($num_columns == 1) { 
						$row = $result->fetchArray(); 
 
						$numrows = $row[ 'numrows' ]; 
						$exists = ($numrows == 1); 
					} 
				} 
				break; 
		} 
 
	} 
 
	// Get results 
	if ($exists) { 
		// Feedback for end user 
		$html .= '<pre>User ID exists in the database.</pre>'; 
	} else { 
		// User wasn't found, so the page wasn't! 
		header( $_SERVER[ 'SERVER_PROTOCOL' ] . ' 404 Not Found' ); 
 
		// Feedback for end user 
		$html .= '<pre>User ID is MISSING from the database.</pre>'; 
	} 
} 
 
// Generate Anti-CSRF token 
generateSessionToken(); 
 
?>