Ajax request is retrieving an empy array in PHP - php

Question

I have a "form" with this code:
<div class="form-wrap" id="contact-form">
<div class="form-innerwrap">
<div class="text-input">
<input type="text" name="name" id="name" required />
<label for="name"><?= CONTACT_FORM_NAME ?></label>
</div>
<div class="text-input">
<input type="email" name="email" id="email" pattern="[a-z0-9._%+-]+#[a-z0-9.-]+\.[a-z]{2,4}$" required />
<label for="email">E-mail</label>
</div>
<div class="text-input">
<input type="text" name="contact" id="contact" required />
<label for="name"><?= CONTACT ?></label>
</div>
<div class="text-input text-textarea">
<textarea type="info" id="info" name="info">
</textarea>
<label for="email"><?= CONTACT_FORM_MENSSAGE ?></label>
</div>
<input type="hidden" name="lang" id="lang" value="<?= $_SESSION['language'] ?>">
<div class="form-button">
<button type="submit" class="btn contacts-button btn-gowe" id="btn-info" data-btnhover="<?= CONTACT_FORM_BTN ?>"> <span><?= CONTACT_FORM_BTN ?></span> </button>
</div>
</div>
</div>
Then I have a ajax request to sent the input values to php:
$("#btn-info").click(function(){
var name = $("#name").val();
var email = $("#email").val();
var contact = $("#contact").val();
var info = $("#info").val();
var lang = $("#lang").val();
// Returns successful data submission message when the entered information is stored in database.
var dataString = 'name='+ name + '&email='+ email +'&contact='+contact+'&info='+info+'&lang='+lang;
$.ajax({
type: "POST",
url: "includes/sendEmail.php",
data: dataString,
cache: false,
success: function(result){
var result = result.split("||");
if (result[0]== "true"){
$("#contact-modal").show();
}
}
});
return false;
});
However when I make a var_dump of $REQUEST the return is an empty array.
Can anyone help me with this problem?
I had already spent several hours to try to understand what is wrong in my code.
Thanks for helping.