通过另一个文件调用PHP函数

I created a simple sample php file for display some function outputs. here is the code..

<?php
// $printName = hello('samitha');
// $printHeader = pageHeader('main','on');

switch (key($_GET)){
    case 'red':
        $printHeader = pageHeader('red','on');
        $printName = hello('Joel');
        break;

    case 'blue':
        $printHeader = pageHeader('blue','off');
        $printName = hello('Duck');
        break;

    case 'yellow':
        //$printHeader = pageHeader('yellow','on');
        break;
}


function hello($name){
    return $name;
}


function pageHeader($header,$onoff){
    if ($onoff == 'on') {
        return $header."page header<br>";
    }
    else {return null;}
}

echo $printHeader;
echo $printName;

?>

This code is working fine without any problems.

When I call 'example.com/php/tipo34.php?red', it shows on the screen:

redpage header
Joel

And when I call 'example.com/php/tipo34.php?blue' it shows on the screen:

Duck

I tried to put the below functions inside of another php file called tipo34-req.php and received the following error:

Fatal error: Call to undefined function pageHeader() in C:\wamp\www\php\tipo34.php on line 8

The code I tried:

<?php
// $printName = hello('samitha');
// $printHeader = pageHeader('main','on');
switch (key($_GET)){
    case 'red':
        $printHeader = pageHeader('red','on');
        $printName = hello('samitha');
        break;

    case 'blue':
        $printHeader = pageHeader('blue','off');
        $printName = hello('kalum');
        break;

    case 'yellow':
        //$printHeader = pageHeader('yellow','on');
        break;
}

include 'tipo34-req.php';

echo $printHeader;
echo $printName;

?>

tipo34-req.php code:

<?php
function hello($name){
    global $name;
    return $name;
}

function pageHeader($header,$onoff){ global $header, $onoff
    if ($onoff == 'on') {
        return $header."page header<br>";
    }
    else {return null;}
}
?>

How do I solve this problem? Using the function directly on the file works, but when I put the functions in another php file, it throws the error.

Thanks.

Include your file above its contents usage. PHP is unaware of the functions since they are included later in the code.

include 'tipo34-req.php';

switch (key($_GET)){
    case 'red':
        $printHeader = pageHeader('red','on');
        $printName = hello('samitha');
    break;

    case 'blue':
        $printHeader = pageHeader('blue','off');
        $printName = hello('kalum');
    break;

    case 'yellow':
        //$printHeader = pageHeader('yellow','on');
    break;


}

echo $printHeader;
echo $printName;

?>

Have you tried including the file at the top before calling any of the functions?