XLIV. Управление функциями

Введение

Эти функции позволяют вам различными способами оперировать функциями.

Требования

Эти функции всегда доступны.

Установка

Для использования этих функций не требуется проведение установки, поскольку они являются частью ядра PHP.

Настройка во время выполнения

Данное расширение не определяет никакие директивы конфигурации в php.ini.

Предопределенные константы

Данное расширение не определяет никакие константы.

Содержание
call_user_func_array -- Вызывает пользовательскую функцию с массивом параметров
call_user_func -- Вызывает пользовательскую функцию
create_function -- Создаёт анонимную (lambda-style) функцию
func_get_arg -- Возвращает элемент из списка аргументов
func_get_args -- Возвращает массив аргументов функции
func_num_args -- Возвращает количество аргументов, переданных функции
function_exists -- Возвращает TRUE, если данная функция определена
get_defined_functions -- Возвращает массив всех определённых функций
register_shutdown_function -- Регистрирует функцию, которая выполняется по завершению работы скрипта
register_tick_function -- Регистрирует функцию для выполнения при каждом тике
unregister_tick_function -- Удаляет функцию из списка зарегистрированных для выполнения при каждом тике

Управление функциями

Michael T. McGrew
12-May-2005 09:56


An interesting way to use functions is by putting other things than PHP in them, i.e. HTML CSS. This can be useful if you will be using a format for many pages. Yes, the include function can be used also, but by defining them in functions can make them more portable in a way and keep you from having to make many include files. You could use include() when one will be putting big portions of PHP, HTML, and/or CSS and will be using them in many pages. Then you could use PHP, HTML, and/or CSS in a function when it is smaller portions of code and only want it to be on a few pages.



I have been using include() for HTML and CSS in my early days of PHP coding, but I will be using functions for that a lot more now.



<?php function a() {  ?>

<style type="text/css">

table { 

border: 1px dashed black; 

background: #95EAFE;

text-align:left;

width:610px;

}

.linkbar {

font-family:sans-serif;

line-height:40px;

top:1px;

text-align:center;

width:200px;

height:10px;

}

</style>

<?php }  ?>



Now doing:

<?php a(); ?>

will return all of the CSS just as if you had wrote it on the actual page, or used include() . The same thing goes for HTML code inside a function. The possibilities are endless...

michael dot bommarito at gmail dot com
30-Jan-2005 11:28


I've developed an easy-to-use hack using these functions to emulate overloaded functions.  It's especially handy for constructors and/or C++ style templating.



Here's a little example to get you going.  This does the trick for most circumstances, and if you need more intelligent parsing, it's not too hard to implement with regex or a more suitable classification scheme.



N.B. Note the lack of whitespace between variable types in case strings.



class Matrix {



...



function Matrix() {

  $args = func_get_args();

  $argmatch = implode(",", array_map('gettype', $args));



  switch( $argmatch ) {

    case 'integer,integer': 

      //initialize m x n matrix

      break;



    case 'integer,integer,integer': 

      //initialize m x n matrix with constant c

      break;



    case 'integer,integer,float': 

      //initialize m x n matrix with constant c

      break;    



    case 'array':

      //initialize from array (2D....)

      break;



    case 'array,integer':

      //intialize from array (1D packed with m rows)

      break;

    

    default:

      //(void) overload?

      //error handling?

      break;

  }

}



...



}

php-note-2003-june-18 at ryandesign dot com
18-Jun-2003 08:22


Xavier's example is rather complicated, and his task would be much more simply accomplished by using classes. Define a base class to do the basic functions open, dump, and close, and create extension classes to override whatever behavior.



class foo {

  function open() {

    // Default functionality for open()

  }

  function dump() {

    // Default functionality for dump()

  }

  function close() {

    // Default functionality for close()

  }

}



class bar extends foo {

  function open() {

    // Override functionality of open()

  }

  // dump() and close() remain as in class foo

}

xmontero at dsitelecom dot com
23-Aug-2002 02:49


You can do some kind of overloading functions in PHP using "function_exists". 



Let's suppose you want a script to call plugins that are php files and you want the plugins to "override" behaviours that if not overriden are used by default.



You might for example write a "mySQL table viewer" which displays a table and it "opens a table", "dumps the header", "dumps row-by-row" and then "closes the table".



Let's suppose you want a plugin for "Stocks" which prints negative stocks in red, so you want to override the "dumping row-by-row" to do that behaviour. Instead you do not want to have all the "default behaviour" repeated in the plugin.



You may then do the following:



1) Define a default plugin (ex: "default.php"



2) Write all your functions in default.php to open, dump and close, but add them a suffix:



open_table_default()

dump_header_default()

dump_row_default()

close_table_default()



3) Call your functions with a wrapper: Insetad of this:

open_table() or open_table_default() write this:



plugincall("open_table");



4) Then write a function called plugincall which uses function_exists() to see if you call one or the other function:



function plugincall($desired_function_name)

{



if( function_exists( $desired_function_name))

{

    //Call the plugin

    //Note the $ before the name

    $desired_function_name()

}

else

{

  $desired_function_name = $desired_function_name . "_default";

  if( function_exists($desired_function_name))

  {

      //Call the default

      //Note the $ before the name

      $desired_function_name()

  }

  else

  {

      // Nor the plugin nor the default were defined

  }

}



So, now, if the require_once(plugin.php) contains a function called "open_table()", it will be used. Instaed, "open_table_default()" will be used.



It's not like overloading functions, but it is very useful to write scripts ampliable by other programmers: If they write a function, it is used, if not, the default is used.



See ya!

Xavier Montero.