$tel = '010-1234-5678';

echo preg_replace('/(\d{3})(-?)(\d{2,})(-?)(\d{4})$/','\1\2****\4\5',$tel);

echo "\n";

$tel = '01012345678';

echo preg_replace('/(\d{3})(-?)(\d{2,})(-?)(\d{4})$/','\1\2****\4\5',$tel);

echo "\n";

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