The Singleton Design Pattern for PHP

By Tony Marston
2005-07-29


A non-class Helper function

This method uses a separate non-class function as a "helper". It contains code similar to the following:

function getDateObject ()

// return the handle to the standard date validation object.

{

    static $instance;

    

    if (!is_object($instance)) {

        // does not currently exist, so create it

        require_once 'std.datevalidation.class.inc';

        $instance = new DateClass;

    } // if

    

    return $instance;

    

} // getDateObject

It is referenced with code similar to the following:

    $dateobj = getDateObject();

This method has the following advantages:

• Because it is designed to work with a single specific class it can also take the responsibility of ensuring that the relevant class file is loaded when necessary.

This method has the following disadvantages:

• It requires a separate helper function for each different class.

Tutorial Pages:
» Introduction
» A non-class Helper function
» A separate Helper method within each class
» A single Helper method for all classes
» References
» Conclusion

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