All fields are not displaying in PHP $_POST as well as $_REQUEST - php

Question

I have a form
<form
method="post"
class="c-form"
action="mail.php"
id="contactform"
>
<div class="row">
<div class="col-lg-12">
<div class="error-alert"></div>
</div>
<div class="col-lg-12">
<input
type="text"
id="subject" name="subject"value="<?php echo $deviceType['device_type_name']; ?> Repair"
/>
</div>
<div class="col-lg-12">
<input
type="text"
placeholder="NAME"
id="name"
name="name"
/>
</div>
<div class="col-lg-12">
<input
type="text"
placeholder="EMAIL"
id="email"
name="email"
/>
</div>
<div class="col-lg-12">
<input
type="text"
placeholder="PHONE NUMBER"
name="phone"
/>
</div>
<div class="col-lg-12">
<textarea
rows="5"
placeholder="YOUR MESSAGE"
id="message"
name="message"
></textarea>
</div>
<div class="col-lg-12">
<input
type="submit"
class="submit"
value="Contact Us"
id="submit"
/>
<img
src="images/ajax-loader.gif"
class="loader"
alt=""
/>
</div>
</div>
</form>
But when I submit the form two fields (subject and message) isn't showing in the $_POST or $_REQUEST array (other 3 fields name, phone and email is present in the array). (the variable $deviceType['device_type_name']; has value, so there is no issue there)
Can anyone please tell me what am I missing here.
mail.php file (nothing much here just for debugging):
<?php
print_r($_POST);
die();?>