How Can I Properly Initialize Complex Static Variables in PHP?

Initializing Static Variables in PHP

When initializing static variables in PHP, you may encounter syntax errors with non-trivial expressions in the initializer, as seen in the code snippet below:

private static $dates = array(
  'start' => mktime( 0,  0,  0,  7, 30, 2009),  // Start date
  'end'   => mktime( 0,  0,  0,  8,  2, 2009),  // End date
  'close' => mktime(23, 59, 59,  7, 20, 2009),  // Date when registration closes
  'early' => mktime( 0,  0,  0,  3, 19, 2009),  // Date when early bird discount ends
);

Workaround:

One solution is to avoid complex expressions in the initializer and instead assign the values after defining the class:

class Foo {
  static $bar;
}
Foo::$bar = array(…);

Another option is to use a static function to initialize the variable:

class Foo {
  private static $bar;
  static function init()
  {
    self::$bar = array(…);
  }
}
Foo::init();

PHP 5.6 Improvement:

PHP 5.6 supports some expressions in static variable initializers. For example, you can define an abstract class with a private static function to initialize the variable:

abstract class Foo{
    private static function bar(){
        static $bar = null;
        if ($bar == null)
            bar = array(...);
        return $bar;
    }
    /* use where necessary */
    self::bar();
}

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