returning variable from function - php

Question

This is probably not the wisest question, but is it possible to return a variable from a function without redeclaring it?
function test(){
$a = 1;
return $a;
}
Would it somehow be possible to access $a with just calling the function? test();
not $a = test();
Is that the only way? I want to make $a available after calling the function.

Answer 1

You have to put the variable into the global scope:
http://codepad.org/PzKxWGbU
function test()
{
$GLOBALS['a'] = 'Hello World!';
}
test();
echo $a;
But it would be better to use a return value or references:
function test(&$ref)
{
$ref = 'Hello World!';
}
$var = '';
test($var);

Answer 2

I assume you want to change some context when you call the function.
This is possible. For example, all global variables share the same context across your application. If a function set's a global variable, its available in the global scope:
function change_global_variable($name, $value)
{
$GLOBALS[$name] = $value;
}
change_global_variable('a', 1);
echo $a;
However, whenever you do something like this, take care that you're destroying the modularity of your code. For example, if you have 50 functions like this and 80 variables, and then you need to change something, you need to change many, many places. And even harder, you don't remember which places you need to change and how they belong to each other.
It's normally better to make the context an object and pass it to the function that changes it, so it's more clear what the function does:
class Context extends ArrayObject {}
$context = new Context;
function change_context(Context $context, $name, $value)
{
$context[$name] = $value;
}
change_context($context, 'b', 2);
echo $context['b'], "\n";
This example demonstrates something that's called dependency injection. Instead of modifying the only one (global) context that exists in PHP, you are telling the function what it should modify, instead that it modifies hard-encoded global variables
There is a mix form of it, using the global variable scope to contain the context, so you spare to pass it as an additional parameter, however I only show it here for completeness, because it's not helping to retain modularity that well (however it's better than using more than one global variable):
class Context extends ArrayObject {}
$context = new Context;
function change_global_context($name, $value)
{
global $context;
$context[$name] = $value;
}
change_global_context('c', 3);
echo $context['c'], "\n";
Rule of thumb: Avoid global variables. Consider them of being very expensive and you don't want your code to be expensive.

Answer 3

No, it is not due to the scoping.
An option would be to declare $a before and then making it a global. It will then be available inside test:
$a = '';
function test(){
global $a;
$a = 1;
return $a;
}
echo $a; // 1
But may I ask why you want to do this? Are you just playing around or do you have a use case? You're most probably doing it wrong if you need this.

Answer 4

Maybe if you just want to show the variable you can use
function test(){
$a = 1;
echo $a;
return $a;
}
in this way if you want you can save the variable $a in a variable if not you can just show it calling the test function.
Hope it helps.
Nicola.