Bruge tidligere defineret variabel inde i en funktion?

Hej. Simpelt spørgsmål:
Hvordan får jeg dette til at virke?
<?php
$MySQL_host  = "localhost";
$MySQL_usr  = "USER";
$MySQL_pwd  = "PASS";
$MySQL_db    = "test";
$pID = $_GET["pageID"];
if (!$pID) {
    $MySQL_query = "SELECT content FROM t_content WHERE id = 2";
} else if ((is_numeric($pID)) && (strlen(($pID) == 1))) {
    $MySQL_query = "SELECT content FROM t_content WHERE id = " .$pID;
} else {
    //Insert exception in here//
}
function db_get_content() {
    mysql_connect($MySQL_host,$MySQL_usr,$MySQL_pwd);
    mysql_select_db($MySQL_db);
    mysql_query($MySQL_query);
}
function contents() {
    $content = db_get_content();
    echo $content;
}
?>