How Can I Properly Initialize Static Variables with Complex Expressions in PHP?

Initialization of Static Variables in PHP

PHP presents a challenge when initializing static variables due to its inability to evaluate non-trivial expressions within initializers. Consider the following code:

private static $dates = array(
  'start' => mktime( 0,  0,  0,  7, 30, 2009),  
  'end'   => mktime( 0,  0,  0,  8,  2, 2009),  
  'close' => mktime(23, 59, 59,  7, 20, 2009),  
  'early' => mktime( 0,  0,  0,  3, 19, 2009),  
);

This code triggers a parse error because PHP expects a ")" after the assignment operator, as seen in the following error message:

Parse error: syntax error, unexpected '(', expecting ')' in /home/user/Sites/site/registration/inc/registration.class.inc on line 19

To circumvent this limitation, we can employ alternative approaches:

1. Deferred Initialization

After defining the class, we can initialize the static variable explicitly using a separate block of code:

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

2. Static Initialization Method

We can define a static method within the class to initialize the variable:

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

Note: PHP 5.6 introduced support for certain expressions in static variable initializers, but this functionality is limited.

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