$re = '/\b(\w+ \w+\b(?: \w+\.)?)/mu';
$str = 'GIVEN:
Paul Millsap Al Horford Tiago Splitter Jeff Teague Kyle Korver Thabo Sefolosha Mike Scott Shelvin Mack Kent Bazemore Dennis Schröder Tim Hardaway Jr. Walter Tavares Justin Holiday Mike Muscala Lamar Patterson Terran Petteway
DESIRED:
Paul Millsap, Al Horford, Tiago Splitter, Jeff Teague, Kyle Korver, Thabo Sefolosha, Mike Scott, Shelvin Mack, Kent Bazemore, Dennis Schröder, Tim Hardaway Jr., Walter Tavares, Justin Holiday, Mike Muscala, Lamar Patterson, Terran Petteway,';
$subst = "\1,";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
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