$re = '/^(\[[^]]+]|\w+) *\. *(\[[^]]+]|\w+)/m';
$str = 'Schema.TableName
Schema . TableName
[Schema].[TableName]
[Schema] . [TableName]
Schema. [TableName]
[SchemaPart1.Part2.Part 3].[Table . Name]';
preg_match_all($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