$re = '/(\s+)?(\[)?database(\])?\.(\[)?dbo(\]?)\.(\[?)table_name(\]?)((\s+)(tn))? (\s+)?/';
$str = ' database.dbo.table_name
database.dbo.table_name tn
[database].[dbo].[table_name]
database.[dbo].[table_name]
database.dbo.[table_name] tn
';
preg_match_all($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