Question

Maybe this is a silly question, but I am very new to PDO and am confused. Is it possible to instantiate a PDO object in one function (open a connection to a server/db) and then close the same connection in another function? Will the functions need to be passed the object to be able to close it? I want to do this so I can create a ubiquitous site-wide function that I can call to start a connection, execute non-generic sql, and then close it with another site-wide function. How can I do this? Do I need to pass the object to these function as arguments?

Answer 1

Yes, this is possible. I’d recommend using a constructor that initiates a connection to MySQL and a destructor that nullifies it. That way, you won’t have to manually call the function every time you want to open and close the connection. The connection will open whenever a new instance of the object is called, and when there are no further references to the object, the connection will be nullified.

It might look something like this:

    private $l; //MySQL Connection

    //Called automatically upon initiation
    function __construct() {
        try {
            $this->l = new PDO("mysql:host=".MYSQL_HOST.";dbname=".MYSQL_DATABASE, MYSQL_USER, MYSQL_PASSWORD); //Initiates connection
            $this->l->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION ); // Sets error mode
        } catch (PDOException $e) {
            file_put_contents("log/dberror.log", "Date: " . date('M j Y - G:i:s') . " ---- Error: " . $e->getMessage().PHP_EOL, FILE_APPEND);
            die($e->getMessage()); // Log and display error in the event that there is an issue connecting
        } 
    }

    //Called automatically when there are no further references to object
    function __destruct() {
        try {
            $this->l = null; //Closes connection
        } catch (PDOException $e) {
            file_put_contents("log/dberror.log", "Date: " . date('M j Y - G:i:s') . " ---- Error: " . $e->getMessage().PHP_EOL, FILE_APPEND);
            die($e->getMessage());
        }
    }

You might find this reference about constructors and destructors useful: http://php.net/manual/en/language.oop5.decon.php