获取PHP函数的多个未定义按钮的名称

I have a backend-edit-site where multiple forms gets created by a while-loop (the number of forms can variegate). Now I want to find out, which button was clicked and use this button-name for a function.

It looks like this:

<?php while($line = mysqli_fetch_array($var)) {?>

   <form id="//echo $line['id']" method="post" action="..">
      <input type="text" value="//echo $line['category']">
      <textarea value="//echo $line['content']">
          //echo $line['content']
      </textarea>

      <button value="//echo $line['id']" name="saveVE //echo $line['id']">Save</button>
   </form>

<?php } ?>

Now I want to make a function like this:

if(isset($_POST['NAME OF THE CLICKED BUTTON'])){
   //some code
}

I only know, that I can get the name of the button by a jquery onClick-event and save it in a javascript variable...

Thanks a lot for your help!

$("body").on('click', '.form_contents button', function(){
  
  var tag = $(this).data('tag');
  
  alert(tag);
  
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
   
<div class="form_contents">
  
  <form id="row1" method="post" action="..">
      <input type="text" value="category1">
      <textarea value="value1">
          value1
      </textarea>

      <button value="SAVE" name="save" data-tag='form1'>Save</button>
   </form>
    .
    .
    .
    .
   <form id="rowN" method="post" action="..">
      <input type="text" value="categoryN">
      <textarea value="valueN">
          value1
      </textarea>

      <button value="SAVE" name="save" data-tag='formN'>Save</button>
   </form>
  
</div>

</div>