$re = '/\|("[^,]+")\|/m';
$str = '(STR,0:30) + |"Outdoor"| + |"Chair Mat","Commercial Floor Mat","Door Mat"| + [Post Type] + (STR,0:30)';
$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