<?php
$input_string = "It is a wonderful goodbye letter that ultimately had a happy ending.";
$array = explode(" ", substr($input_string,0,-1));
array_push($array, "-");
for($i=0;$i<4;$i++)
   array_unshift($array, array_pop($array));
$output_string = ucfirst(implode(" ", $array)) . ".";
print_r($output_string);
?>

A happy ending - It is a wonderful goodbye letter that ultimately had.