Code:
<?php
$company='bizhat';
$sent=' HEY buddy how are you doing';
echo 'hey '.ucwords($company.' is cooler THAN ANYTHING.'). strtolower(str_replace('buddy', 'man', $sent));

echo '<br>'.str_replace('HEY','',$sent); // here str_replace is used to delete a word.
in the last code str_replace is used to delete word.

http://php.flashwebhost.com/austin/day3.php