Image is not updated but redirecting to code.php

Here is my code: employee_edit.php
<div class="modal-body">
<?php

if(isset($_POST['emp_edit_btn'])) {
    $emp_edit_id= $_POST['emp_edit_id'];
    $query="SELECT * FROM employee WHERE eid='$emp_edit_id'";
    $query_run=mysqli_query($conn,$query);

    foreach($query_run as $rowEdit) {
?>
          
          
    <form action="code.php" method="POST" enctype="multipart/form-data">
        <input type="hidden" name="emp_update_id" value="<?php echo $rowEdit['eid']?>">

        <hr style="border-top: 1px solid #ccc; background: transparent;">
        <h5>Personal Details</h5>
        <hr style="border-top: 1px solid #ccc; background: transparent;">
        <div class="form-group">
            <label>Name</label>
            <input type="text" name="emp_edit_name" value="<?php echo $rowEdit['emp_name']?>" class="form-control">
        </div>
        <div class="form-group">
            <label>Date of Birth</label>
            <input type="date" name="emp_edit_dob" value="<?php echo $rowEdit['emp_dob']?>" class="form-control" >
        </div>

<div class="form-group">
        Employee Image
                        
        
         

        
    </div> 
                      
    
    " height = 90px width = 90px >
    <br>
    <div> 
        Update
        <a href="employee.php" class="btn btn-danger">Cancel</a>
    </div> 

code.php:

if(isset($_POST['emp_updatebtn'])){
    $emp_update_id=$_POST['emp_update_id'];
    $emp_name=$_POST['emp_edit_name'];
    $emp_dob=$_POST['emp_edit_dob'];
    $emp_gender=$_POST['emp_edit_gender'];
    $emp_national=$_POST['emp_edit_national'];
    $emp_phone=$_POST['emp_edit_phone'];
    $emp_email=$_POST['emp_edit_email'];
    $emp_curr_add=$_POST['emp_edit_currAdd'];
    $emp_perm_add=$_POST['emp_edit_permAdd'];
    $s_id=$_POST['s_id_edit'];
    $c_id=$_POST['c_id_edit'];
    $emp_start=$_POST['emp_edit_start'];
    $emp_as=$_POST['emp_edit_empAs'];
    $emp_job_id=$_POST['emp_edit_jobID'];
    $emp_end=$_POST['emp_edit_end'];
    $emp_status=$_POST['emp_edit_status'];

    $emp_edit_conPerson=$_POST['emp_edit_conPerson'];
    $emp_edit_rlt=$_POST['emp_edit_rlt'];
    $emp_edit_emerPhone=$_POST['emp_edit_emerPhone'];
    $emp_edit_emerEmail=$_POST['emp_edit_emerEmail'];
    $emp_edit_bankName=$_POST['emp_edit_bankName'];
    $emp_edit_accName=$_POST['emp_edit_accName'];
    $emp_edit_accNum=$_POST['emp_edit_accNum'];

    $emp_img_old=$_POST['emp_img_old'];
    $emp_img_new=$_FILES['emp_img']['name'];

    if($emp_img_new!=''){
        $update_img= $_FILES['emp_img']['name'];
    } else {
        $update_img= $emp_img_old; 
    }

    if ($_FILES['emp_img']['name']!='') {
        if (file_exists("emp_upload/" . $_FILES['emp_img']['name'])) {
            $img=$_FILES['emp_img']['name'];
            $_SESSION['status']="img exists".$img;
            header("Location:employee.php");
        }
    } else {

        $query="UPDATE employee 
                    SET emp_name='$emp_name', 
                    emp_dob='$emp_dob', 
                    emp_gender='$emp_gender',
                    emp_national='$emp_national',
                    emp_phone='$emp_phone',
                    emp_email='$emp_email',
                    emp_curr_add='$emp_curr_add',
                    emp_perm_add='$emp_perm_add',
                    s_id='$s_id',
                    c_id='$c_id',
                    emp_start='$emp_start',
                    emp_as='$emp_as',
                    emp_job_id='$emp_job_id',
                    emp_end='$emp_end',
                    emp_status='$emp_status',
                    contact_person='$emp_edit_conPerson',
                    rlt='$emp_edit_rlt',
                    emer_phone='$emp_edit_emerPhone',
                    emer_email='$emp_edit_emerEmail',
                    bank_name='$emp_edit_bankName',
                    acc_name='$emp_edit_accName',
                    acc_num='$emp_edit_accNum',
                    emp_img='$update_img'  
                WHERE eid='$emp_update_id'";

        $query_run=mysqli_query($conn,$query);

        if($query_run){
            if($_FILES['emp_img']['name']!= '') {
                move_uploaded_file($_FILES['emp_img']['tmp_name'], "emp_upload/".$_FILES['emp_img']['name']);
                unlink ('emp_upload/'.$img_name_old );
            }

            $_SESSION['success']="Your data is Updated";
            header("Location:employee.php");
        } else{
            $_SESSION['status']="Your data is NOT Updated";
            header("Location:employee.php");

        }   
    }
}</div>