Код который посылает запрос к контроллеру и получает ответ
<script>
	(function($) {
		$(document).ready(function(){
			if( $('#wpforms-form-446').length ) {
				$('#wpforms-submit-446').prop('disabled', true);
				$('#wpforms-446-field_21, #wpforms-446-field_3').change(function(){
					check();
				});
				$('#wpforms-form-446 .wpforms-field-container').append('<div id="errs"></div>');
				$('#wpforms-submit-446').click(function(event){
					if( $('#wpforms-submit-446').prop('disabled') )
						return;
					let email = $('#wpforms-446-field_3').val();
					let phone = $('#wpforms-446-field_21').val();
					let password = $('#wpforms-446-field_4').val();
					let name = $('#wpforms-446-field_1').val();
					if( email.length == 0 || phone.length == 0 )
						return;
					$.ajax({
					  method: "POST",
						dataType : 'json',
					  url: "/api.php?create-user",
					  data: { email: email, phone: phone, password: password, name: name }
					})
				  .success(function( msg ) {
						$('#errs').html('');
						console.log(msg)
				  });
				});
				function check() {
					let email = $('#wpforms-446-field_3').val();
					let phone = $('#wpforms-446-field_21').val();
					if( email.length == 0 || phone.length == 0 )
						return;
					$.ajax({
					  method: "POST",
						dataType : 'json',
					  url: "/api.php?has-user",
					  data: { email: email, phone: phone }
					})
				  .success(function( msg ) {
						$('#errs').html('');
						let b_error = false;
						if( msg.error !== undefined ) {
							let error = msg.error;
							for (var variable in error) {
								b_error = true;
								$('#errs').append('<label class="wpforms-error">'+error[variable]+'</label>');
							}
						}
						else {
							if( msg.result !== undefined && msg.result == true ) {
								b_error = true;
								$('#errs').append('<label class="wpforms-error">Пользователь существует. <a href="https://a-n-h.space/rm_login/">Войти</a></label>');
							}
						}
						if( b_error == false ) {
							$('#wpforms-submit-446').prop('disabled', false);
						}
				  });
				}
			}
		});
	})( jQuery );
</script>