If, by multiple returns, you mean more than one return statement in the function, then there must be something else wrong with your code. Try this, it will display Hello World:
<?
function testReturn ($theParameter) {
if ( $theParameter == 1) {
return "Hello";
} else {
return "World";
}
}
echo testReturn (1) . " ";
echo testReturn (2) . "<br>";
?>