Function not returning

I have the following 2 scripts...

//functions.php
<?php
function test($mike) {
if ($mike = "hello"){
$reply = "you said hello";
return $reply;
} else {
$reply = "you didn't say hello";
return $reply;
}
}
?>

//test.php
<?php
include("functions.php");
$mike = "hello";
test($mike);
echo $reply;
?>

When I run test.php I don't get anything, blank screen.

What would I be doing wrong?

Thanks Mike

.