$re = '/{{((\w+)(.\w+|\[\d+\])+?)}}/';
$str = 'Sayın {{test.ate}} {{Name.Test[1]}} {{Surname.Test[1].Test}} {{a[0].test}} {{a[0].test[0]}} {{a[0].test[0].Yunus[0].Surname}} {{a.a[1][1]}} {{test[1][1][1312312].Test[0].tes.test.tes}} bla bla bla';
preg_match_all($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