How to initialize static variables

Svish_39321 0
Viewed 216101

I have this code:

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
);

Which gives me the following error:

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

So, I guess I am doing something wrong... but how can I do this if not like that? If I change the mktime stuff with regular strings, it works. So I know that I can do it sort of like that..

Anyone have some pointers?

class static-members php
9 Answers

PHP can't parse non-trivial expressions in initializers.

I prefer to work around this by adding code right after definition of the class:

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

or

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

PHP 5.6 can handle some expressions now.

/* For Abstract classes */
abstract class Foo{
    private static function bar(){
        static $bar = null;
        if ($bar == null)
            bar = array(...);
        return $bar;
    }
    /* use where necessary */
    self::bar();
}
user_270090

If you have control over class loading, you can do static initializing from there.

Example:

class MyClass { public static function static_init() { } }

in your class loader, do the following:

include($path . $klass . PHP_EXT);
if(method_exists($klass, 'static_init')) { $klass::staticInit() }

A more heavy weight solution would be to use an interface with ReflectionClass:

interface StaticInit { public static function staticInit() { } }
class MyClass implements StaticInit { public static function staticInit() { } }

in your class loader, do the following:

$rc = new ReflectionClass($klass);
if(in_array('StaticInit', $rc->getInterfaceNames())) { $klass::staticInit() }
user_2220150

That's too complex to set in the definition. You can set the definition to null though, and then in the constructor, check it, and if it has not been changed - set it:

private static $dates = null;
public function __construct()
{
    if (is_null(self::$dates)) {  // OR if (!is_array(self::$date))
         self::$dates = array( /* .... */);
    }
}
user_62160

You can't make function calls in this part of the code. If you make an init() type method that gets executed before any other code does then you will be able to populate the variable then.

alxp_195130
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