$re = '/^\s*\w+(?: +\w+)*(?:\s*, *\w+(?: +\w+)*)+\s*$/m';
$str = ' 1000,two thousand,3000
1000 , 2000 , 3000
First Option,2Nd Option, THIRD Option
Single Value
1000 ,, 2000 , 3000
1000 , 2000 , 3000,
1000 , 2000 , 3000,,
,,1000 , 2000 , 3000';
preg_match_all($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