$re = '/^Examples of fruits are (?>((?>bananas|apples|grapes|pears))(?![^.]*?\b\1\b)(?>,\s*+|\s++and\s++)?)++\.$/m';
$str = 'Examples of fruits are apples, bananas, pears and grapes.
Examples of fruits are apples, bananas, grapes and pears.
Examples of fruits are bananas, pears and grapes.
Examples of fruits are apples, bananas, pears and pears.
Examples of fruitz are apples, bananas, pears and grapes.
Examples of fruits are kiwis, apples, bananas, pears and grapes.';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php