Q:

How do I make a variable from outside a function work in that function?

function nothing() { 
    echo $variableThatIWant; 
}

A:

The better way is to pass it as an argument.
function nothing($var) {
    echo $var;
}

$foo = 'foo';
nothing($foo);

The evil way, and I dont know why I'm even showing you this, is to use global.
function nothing() {
    global $foo;
    echo $foo;
}

$foo = 'foo';
nothing();

A:

You can put "global" before the variable you want to use, Like this :
<?php
    $txt = "Hello";
    function Test() {
        global $txt;
        echo $txt;
    }
    Test();
?>

OR :
you can passed it as parameter, Like this :
<?php
    $txt = "Hello";
    function Test($txt) {
        echo $txt;
    }
    Test($txt);
?>

source : http://browse-tutorials.com/tutorial/php-global-variables

A:

You have to use global.
$var = 'hello';

function myprint()
{
   global $var;
   echo $var;
}

