将行ID设置为递增，因此没有重复项

Question

I have a table that has an ID that basically auto-increments. I have IDs up to 221. I have an add row function that adds rows and gives the row an ID based on how many rows there are. So if I delete a row and there are only 220 rows now, and once I add a row, the ID will be 221. However, there was already a 221 ID so no matter how many rows I delete, I want the ID to start at 222 and continue to go up from there. How would I do this?

HTML/PHP:

<table id="html_master">
<thead>
    <tr>
    <td>ID</td>
    <td>Vendor</td>
    <td>Buyer ID</td>
    <td>POC Name</td>
    <td>POC Email</td>
    <td>POC Phone</td>
    <td>Edit/Delete</td>
    </tr>
</thead>
<tbody>

<?php
    foreach ($dbh->query($sql) as $rows){
    ?>
    <tr>
        <td class="mr_id" contenteditable="false"><?php echo intval ($rows['MR_ID'])?></td>
        <td class="mr_name" contenteditable="false"><?php echo $rows['MR_Name']?></td>
        <td class="buyer_id" contenteditable="false"><?php echo $rows['Buyer_ID']?></td>
        <td class="poc_n" contenteditable="false"><?php echo $rows['MR_POC_N']?></td>     
        <td class="poc_e" contenteditable="false"><?php echo $rows['MR_POC_E']?></td>
        <td class="poc_p" contenteditable="false"><?php echo $rows['MR_POC_P']?></td>
        <td><button class="edit" name="edit">Edit</button>
        <button class="delRow" name="delete" onclick="deleteRow(this)">Delete</button></td>
        </tr>
 <?php
  }
 ?>
</tbody>
        <br>
        <input type="button" class="add" value="Add Row" onclick="addRow('html_master')">  
</table>

Javascript for adding row:

function addRow(tableID) {

    var table = document.getElementById(tableID);

    var rowCount = table.rows.length;
    var row = table.insertRow(rowCount);

    var cell1 = row.insertCell(0);
    cell1.innerHTML = rowCount;

    var cell2 = row.insertCell(1);
    var element2 = document.createElement("input");
    element2.type = "text";
    element2.name = "txtbox[]";
    cell2.appendChild(element2);

    var cell3 = row.insertCell(2);
    var element3 = document.createElement("input");
    element3.type = "text";
    element3.name = "txtbox[]";
    cell3.appendChild(element3);

    var cell4 = row.insertCell(3);
    var element4 = document.createElement("input");
    element4.type = "text";
    element4.name = "txtbox[]";
    cell4.appendChild(element4);

    var cell5 = row.insertCell(4);
    var element5 = document.createElement("input");
    element5.type = "text";
    element5.name = "txtbox[]";
    cell5.appendChild(element5);

    var cell6 = row.insertCell(5);
    var element6 = document.createElement("input");
    element6.type = "text";
    element6.name = "txtbox[]";
    cell6.appendChild(element6);

    var cell7 = row.insertCell(6);
    var element7 = document.createElement("input");
    var element8 = document.createElement("input")
    element7.type = "button";
    element8.type = "button";
    element7.name="edit";
    element8.name="del"
    element7.value="Edit";
    element8.value="Delete";
    cell7.appendChild(element7);
    cell7.appendChild(element8);
}