php - Auto increment employee ID -

i want add employee , after that, employee id increment. textbox must disabled

also here's code. want auto increment employee id when add new employee. hope me. thank in advance. :)

<center>     <form class="contact_form" action="#" method="post">             <h2>register new employee</h2>             <br/>             <table>                 <tr>             <td><label for="emp">emp id:</label></td>             <td><input type="text" name="emp" placeholder="emp id" required /></td>         </tr>                 <tr>             <td><label for="name">name:</label></td>             <td><input type="text" name="fname" placeholder="first name" required />                     <input type="text" name="lname" placeholder="last name" required /></td>         </tr>         <tr>             <td><label for="address">address:</label></td>             <td><input type="text" name="address" placeholder="full address" required /></td>         </tr>         <tr>             <td><label for="contact">contact:</label></td>             <td><input type="text" name="contact" placeholder="contact number" required /></td>         </tr>                 <tr>                     <td><label for="type">type:</label></td>                     <td><select name="type" id="type">                         <option>type of employee</option>                         <option>contractual</option>                         <option>regular</option>                     </select>                     </td>                 </tr>                 <tr>             <td><label for="salary">salary:</label></td>             <td><input type="text" name="salary" placeholder="emp salary" required /></td>         </tr>         </table>             <br/>             <button class="submit" name="submit" type="submit" onclick="message()">submit</button>             <button class="reset" name="reset" type="reset">clear</button>         </form>         <?php         if (isset($_post['submit'])) {             include 'alqdb.php';                 $emp=$_post['emp'];                 $fname= $_post['fname'];                 $lname=$_post['lname'];                 $address=$_post['address'];                 $contact=$_post['contact'];                 $type=$_post['type'];                 $salary=$_post['salary'];             mysqli_query($con, "insert employee (empid,empfname,emplname,empaddress,contactnumber,typeofemployee,salary)             values ('$emp','$fname','$lname','$address','$contact','$type','$salary')");         }         ?>     </center> </body> <script language="javascript">     function message() {         alert("successfully added!");     } </script> 

if want have empid emp001

this code work:

public function autoincemp()

{     global $value2;     $query = "select empid tbemployee order empid desc limit 1";     $stmt = $this->db->prepare($query);     $stmt->execute();      if ($stmt->rowcount()>0)     {     $row=$stmt->fetch(pdo::fetch_assoc);          $value2 =$row['empid'];         $value2 =substr($value2,3,5);         $value2 = (int)$value2 + 1;         $value2 = "emp". sprintf('%04s',$value2);  $value = $value2;    return $value;     }     else {         $value2 = "emp0001";         $value = $value2;     return $value;     }     }