PHP全局关键字里面的功能不起作用

Question

考虑以下代码

// Grab some values to be used later ('Y' or 'N')
$daycareactive = isActiveProgramType($companyid,'daycare');
$oscactive = isActiveProgramType($companyid,'osc');
$preschoolactive = isActiveProgramType($companyid,'preschool');
$ecsactive = isActiveProgramType($companyid,'ecs');
$grouphomeactive = isActiveProgramType($companyid,'grouphome');
$dayhomeactive = isActiveProgramType($companyid,'dayhome');
$otheractive = isActiveProgramType($companyid,'other');

echo "Daycare Active 1: ".$daycareactive;

function setFirstAvailablePage(){
   global $daycareactive, $oscactive, $preschoolactive, $ecsactive, $grouphomeactive, $dayhomeactive, $otheractive;

   echo "Daycare Active 2: ".$daycareactive;

   ...other stuff goes here
}

以上结果如下：

Daycare Active 1: N
Daycare Active 2:

为什么第二个空白？

我正在使用关键字global，所以据我所知，它应该引入在此函数之外定义的变量。为什么不起作用？