Question

I wrote a class to create an automated connection with MySQL and create queries. Here’s how it looks like:

include("constants.php");

class MySQLDB {
    var $connection;

    function __construct() {
        $this->connection = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die(mysql_error());
        mysql_select_db(DB_NAME, $this->connection);
        mysql_set_charset('utf8', $this->connection);
    }

    // SELECT ALL FROM
    function sf($unit, $table) {
        return mysql_query("SELECT ".$unit." FROM ".$table, $this->connection);
    }
        // and so on...
}

$mysql = new MySQLDB;

Now, I thought it would be better if I close the connection after I run some of this functions in other php pages. So how do I do that (the most effective way) in this class?

I tried adding mysql_close($this->connection); at the end of the class (before the close bracket) but it gives me an error.

Answer 1

You’d need to place that code in a function named __destruct(), much in the same way as __construct(). See http://php.net/manual/en/language.oop5.decon.php for more information.

The code would then look like:

include("constants.php");

class MySQLDB {
    var $connection;
    var $sf;

    function __construct() {
        $this->connection = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die(mysql_error());
        mysql_select_db(DB_NAME, $this->connection);
        mysql_set_charset('utf8', $this->connection);
    }

    // SELECT ALL FROM
    function sf($unit, $table) {
        return mysql_query("SELECT ".$unit." FROM ".$table, $this->connection);
        $this->sf();
    }
        // and so on...

    function __destruct() {
        mysql_close($this->connection);
    }
}

Please note that you don’t know exactly when this method is run: that depends on when the object is garbage collected. But as Ken noted below, executing mysql_close() is good for symmetry, but not necessary to free resources.