How to access an argument of the "parent" function? [duplicate]

Question

For example I have the following code:

function a($param) { function b() { echo $param; } b(); } a("Hello World!");

That throws an E_NOTICE error because $param is of course undefined (in b()).

I cannot pass $param to b() because b() should be a callback function of preg_replace_callback(). So I had the idea to save $param in $GLOBALS.

Is there any better solution?

FYI, b would be called a closure if it has access to $param. — user395760
– user395760, Commented Jul 16, 2011 at 15:08
@Felix Kling: None, why are you asking? Closures are a language-agnostic concept. — user395760
– user395760, Commented Jul 16, 2011 at 15:12

Ondrej Slinták · Accepted Answer · 2011-07-16 15:09:26Z

12

If you are using PHP 5.3, you could use anonymous function with use keyword instead:

<?php function a($param) { $b = function() use ($param) { echo $param; }; $b(); } a("Hello World!");

answered Jul 16, 2011 at 15:09

Ondrej Slinták

32.1k21 gold badges97 silver badges127 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Travis Weston Over a year ago

I'd never seen this functionality before. +1 for teaching me something new here.

Ryan Culpepper · Accepted Answer · 2011-07-16 19:53:56Z

BTW, since this was tagged functional-programming: in most functional programming languages, you would just refer to param, and it would be in scope, no problem. It's called lexical scoping, or sometimes block scoping.

It's typically languages without explicit variable declarations (eg "assign to define") that make it complicated and/or broken. And Java, which makes you mark such variables final.

Travis Weston · Accepted Answer · 2011-07-16 15:10:21Z

I'd suggest using objects here.

Class a { private $param; private static $instance; public function __construct($param){ $this->param = $param; self::$instance = $this; } public function getParam(){ return $this->param; } public static function getInstance(){ return self::$instance; } } function b(){ echo a::getParam(); }

Memochipan · Accepted Answer · 2011-07-16 15:21:32Z

0

I suggest the use of each function lonely, and call the second function from the first function passing parameters.

It do your code more clear because each function do a single set of operations.

<?php function a($param) { b($param); } function b($param) { echo $param; } a("Hello World!"); ?>

edited Jul 16, 2011 at 15:21

answered Jul 16, 2011 at 15:12

Memochipan

3,4735 gold badges38 silver badges62 bronze badges

5 Comments

ComFreek Over a year ago

But I want to use b() as a callback function of preg_replace_callback. So with your solution I have to make $param globally available.

Memochipan Over a year ago

Maybe these links help you: [stackoverflow.com/questions/48947/… and [stackoverflow.com/questions/4016264/php-callback-functions]

Memochipan Over a year ago

Maybe you must consider other alternatives since the solution above by Ondrej Slinták only works in PHP 5.3. In PHP 5.2 it returns parse error in line 4.

ComFreek Over a year ago

Yes, but the script I build only minimizes my own scripts (so 5.3.1). But how would look an alternative with preg_replace_callback? Can you give me an example?

Memochipan Over a year ago

Before PHP 5.3 create_function() was used. php.net/manual/en/function.create-function.php

Collectives™ on Stack Overflow

How to access an argument of the "parent" function? [duplicate]

4 Answers 4

1 Comment

Comments

Comments

5 Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

Comments

Comments

5 Comments

Linked

Related