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Last updated: Thu, 21 Aug 2003

XXXIII. Function Handling functions


These functions all handle various operations involved in working with functions.


No external libraries are needed to build this extension.


There is no installation needed to use these functions; they are part of the PHP core.

Runtime Configuration

This extension has no configuration directives defined in php.ini.

Predefined Constants

This extension has no constants defined.

Table of Contents
call_user_func_array --  Call a user function given with an array of parameters
call_user_func --  Call a user function given by the first parameter
create_function -- Create an anonymous (lambda-style) function
func_get_arg -- Return an item from the argument list
func_get_args --  Returns an array comprising a function's argument list
func_num_args --  Returns the number of arguments passed to the function
function_exists --  Return TRUE if the given function has been defined
get_defined_functions --  Returns an array of all defined functions
register_shutdown_function --  Register a function for execution on shutdown
register_tick_function --  Register a function for execution on each tick
unregister_tick_function --  De-register a function for execution on each tick

add a note add a note User Contributed Notes
Function Handling functions
php-note-2003-june-18 at ryandesign dot com
18-Jun-2003 10:22
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
24-Aug-2002 04:49
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:


3) Call your functions with a wrapper: Insetad of this:
open_table() or open_table_default() write this:


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 = $desired_function_name . "_default";
  if( function_exists($desired_function_name))
      //Call the default
      //Note the $ before the name
      // 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.

 Last updated: Thu, 21 Aug 2003
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