$re = '`^(.(?:\. *| +))([\p{L}\p{N}\p{M}]+)`m';
$str = 'Ą.BČ
Ą.BČ D Ę
Ą. BČ
Ą. BČ D Ę
Ą BČ
Ą BČ D Ę
Examples below should not be affected.
ĄB ČD DĘ';
$subst = "$2 $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