AJAX - Form Validation with PHP

form.html

<form  action="process.php" method="post">
  <label>First Name</label>
  <input name="first_name" type="text"  />
  <label>Email</label>
  <input name="email" type="text"  />
  <input type="submit" value="Submit" />
</form>


<script>
var data = {};
$(document).ready(function() {
  $('input[type="submit"]').on('click', function() {
      resetErrors();
      var url = 'process.php';
      $.each($('form input, form select'), function(i, v) {
          if (v.type !== 'submit') {
              data[v.name] = v.value;
          }
      }); //end each
      $.ajax({
          dataType: 'json',
          type: 'POST',
          url: url,
          data: data,
          success: function(resp) {
              if (resp === true) {
                  	//successful validation
                      $('form').submit();
                  	return false;
              } else {
                  $.each(resp, function(i, v) {
	        console.log(i + " => " + v); // view in console for error messages
                      var msg = '<label class="error" for="'+i+'">'+v+'</label>';
                      $('input[name="' + i + '"], select[name="' + i + '"]').addClass('inputTxtError').after(msg);
                  });
                  var keys = Object.keys(resp);
                  $('input[name="'+keys[0]+'"]').focus();
              }
              return false;
          },
          error: function() {
              console.log('there was a problem checking the fields');
          }
      });
      return false;
  });
});
function resetErrors() {
    $('form input, form select').removeClass('inputTxtError');
    $('label.error').remove();
}
</script>

process.php

session_start();
if(isset($_POST)){
  	if (empty($_POST['first_name'])) {
		$_SESSION['errors'][‘first_name'] = ‘First name is missing’;
        	}
	if (empty($_POST[‘email’])) {
		$_SESSION['errors'][‘email'] = ‘email is missing’;
        	}
 
        if(count($_SESSION['errors']) > 0){
	    //This is for ajax requests:
            if(!empty($_SERVER['HTTP_X_REQUESTED_WITH']) &&  strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') {
                echo json_encode($_SESSION['errors']);
                exit;
             }
	    //This is when Javascript is turned off:
           echo “<ul>”;
           foreach($_SESSION['errors'] as $key => $value){
	      echo “<li>” . $value . “</li>”;
           }
           echo “</ul>”;exit;
    }else{
	//form validation successful - process data here!!!!
   }
}