
<!DOCTYPE html>
<html>
<body>

<?php
function sum($x,$y) {
   $z=$x+$y;
   return $z;
}

echo "5 + 10 = " . sum(5,10) . "<br>";
echo "7 + 13 = " . sum(7,13) . "<br>";
echo "2 + 4 = " . sum(2,4);
?>

</body>
</html>