<form action="" method="GET">
<input type="submit" name="submit" value="Сохранить" />
</form><form action="" method="GET">
<button type="submit" name="submit" class="btn border-slate text-slate-800 btn-flat">Сохранить</button>
</form><?php
if($_GET['submit']){ бла бла }if($_GET['submit']){ бла бла }используйтеif(isset($_GET['submit'])){ бла бла }