Button for insert operation is not working
code: html
 <form method= "post " action="">  
   Experiment name : <input type="text" name="exp_name" placeholder="Enter exp Name" Required>
  <br/>
  Exp Date : <input type="text" name="exp_date" placeholder="Enter date" Required>
  <br/>
  sbst name : <input type="text" name="sb_name" placeholder="Enter sb name" Required>
  <br/>
  sbst id : <input type="text" name="sb_id" placeholder="Enter sb id" Required>
  <br/>
   Exp TIME : <input type="text" name="exp_time" placeholder="Enter time" Required>
  <br/>
   machine : <input type="text" name="machine_name" placeholder="Enter mach name" Required>
  <br/>
   incharge : <input type="text" name="exp_incharge" placeholder="Enter incharge" Required>
  <br/>
   team : <input type="text" name="exp_team" placeholder="Enter team" Required>
  <br/>
  <input type="submit" name="submit" value="Submit">
   </form>php:
<?php
    include 'db_con.php';
    $conn = OpenCon(); // establish connection
    echo "Connected Successfully";
    
    if(isset($_POST['submit']))
    {
        $Exp_name = $_POST['exp_name'];
        $Exp_date = $_POST['exp_date']; 
        $Subset_name = $_POST['sb_name'];
        $Subset_id = $_POST['sb_id'];
        $Exp_time = $_POST['exp_time'];
        $machine = $_POST['machine_name'];
        $Exp_Incharge = $_POST['exp_incharge'];
        $Exp_team = $_POST['exp_team'];
        
        $sql = "INSERT INTO pre_exp_details (
Exp_Name,
Exp_Date,
Subset_Name,
Subset_ID,
Exp_Time,
Machine,
Exp_Incharge,
Exp_Team)
        
 VALUES (
'$Exp_name ',
'$Exp_date',
'$Subset_name',
'$Subset_id',
'$Exp_time',
'$machine',
'$Exp_Incharge',
'$Exp_team')";
      
        
            if(mysqli_query($conn, $sql)){
                echo "Records inserted successfully.";
            } else{
                echo "ERROR: Could not able to execute $sql. ". mysqli_error($conn);
            }
            mysqli_close($conn);
      
    }
?>