สมมติผมมีไฟล์ configuration database แค่ตัวเดียว (PDO.php)
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class configDatabase
{
public static $DB_DSN = "mysql:host=localhost;dbname=api"; // set host name and database name
public static $DB_USERNAME = "root"; // set user name
public static $DB_PASSWORD = "12345678"; // set password