Static class initializer in PHP

Question

I have an helper class with some static functions  All the functions in the class require a    heavy    initialization function to run once  as if it were a constructor    Is there a good practice for achieving this   The only thing I thought of was calling an init function  and breaking its flow if it has already run once  using a static  initialized var   The problem is that I need to call it on every one of the class   s functions

User · Accepted Answer

Sounds like you d be better served by a singleton rather than a bunch of static methods  class Singleton                     var Singleton         private static  instance     private function   construct              Your  heavy  initialization stuff here        public static function getInstance           if   is null  self   instance                 self   instance   new self              return self   instance         public function someMethod1              whatever        public function someMethod2              whatever         And then  in usage     As opposed to this Singleton  someMethod1        You d do this Singleton  getInstance  - gt someMethod1

User · Answer

Note - the RFC proposing this is still in the draft state     class Singleton       private static function   static                                           proposed for PHP 7 x  see https   wiki php net rfc static class constructor

User · Answer

Actually  I use a public static method   init     on my static classes that require initialization  or at least need to execute some code    Then  in my autoloader  when it loads a class it checks is callable  class     init       If it is  it calls that method   Quick  simple and effective

User · Answer

If you don t like public static initializer  reflection can be a workaround    lt  php  class LanguageUtility       public static function initializeClass  class                try                          Get a static method named  initialize   If not found                 ReflectionMethod   will throw a ReflectionException               ref   new  ReflectionMethod  class   initialize                    The  initialize  method is probably  private                  Make it accessible before calling  invoke                  Note that  setAccessible  is not available                before PHP version 5 3 2               ref- gt setAccessible true                   Execute the  initialize  method               ref- gt invoke null                        catch  Exception  e                               class MyClass       private static function initialize                  LanguageUtility  initializeClass  MyClass       gt

User · Answer

I am posting this as an answer because this is very important as of PHP 7 4   The opcache preload mechanism of PHP 7 4 makes it possible to preload opcodes for classes  If you use it to preload a file that contains a class definition and some side effects  then classes defined in that file will  exist  for all subsequent scripts executed by this FPM server and its workers  but the side effects will not be in effect  and the autoloader will not require the file containing them because the class already  exists   This completely defeats any and all static initialization techniques that rely on executing top-level code in the file that contains the class definition

User · Answer

file Foo php class Foo     static function init                    Foo  init      This way  the initialization happens when the class file is included  You can make sure this only happens when necessary  and only once  by using autoloading

User · Answer

There is a way to call the init   method once and forbid it s usage  you can turn the function into private initializer and ivoke it after class declaration like this   class Example       private static function init                do whatever needed for class initialization          static function          static  init      - gt bindTo null  Example  class

User · Answer

NOTE  This is exactly what OP said they did   But didn t show code for   I show the details here  so that you can compare it to the accepted answer  My point is that OP s original instinct was  IMHO  better than the answer he accepted   Given how highly upvoted the accepted answer is  I d like to point out the  quot naive quot  answer to one-time initialization of static methods  is hardly more code than that implementation of Singleton -- and has an essential advantage  final class MyClass        public static function someMethod1             MyClass  init               whatever            public static function someMethod2             MyClass  init               whatever             private static  didInit   false       private static function init             if   self   didInit                self   didInit   true                 one-time init code                          private  so can t create an instance      private function   construct                Nothing to do - there are no instances           The advantage of this approach  is that you get to call with the straightforward static function syntax  MyClass  someMethod1     Contrast it to the calls required by the accepted answer  MyClass  getInstance- gt someMethod1     As a general principle  it is best to pay the coding price once  when you code a class  to keep callers simpler   If you are NOT using PHP 7 4 s opcode cache  then use Victor Nicollet s answer  Simple  No extra coding required  No  quot advanced quot  coding to understand   I recommend including FrancescoMM s comment  to make sure  quot init quot  will never execute twice   See Szczepan s explanation of why Victor s technique won t work with opcode cache  If you ARE using opcode cache  then AFAIK my answer is as clean as you can get  The cost is simply adding the line MyClass  init    at start of every public method  NOTE  If you want public properties  code them as a get   set pair of methods  so that you have a place to add that init call   Private members do NOT need that init call  as they are not reachable from the outside - so some public method has already been called  by the time execution reaches the private member

[php] Static class initializer in PHP

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