PHP: Function Handling functions - Manual
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Last updated: Wed, 29 Jan 2003

XXXIV. Function Handling functions

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

차례
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


User Contributed Notes
Function Handling functions
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xmontero at dsitelecom dot com
23-Aug-2002 09:49

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.

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<ftp_systypecall_user_func_array>
 Last updated: Wed, 29 Jan 2003
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