<form id="settingsFrm" name="settingsFrm" method="POST" action="saveSettings.php">
	<input type="hidden" name="tHeaderText" value="New Title" />
	<input type="hidden" name="cHeaderText" value="" />
	<input type="hidden" name="cHeaderBackground" value="" />
	<input type="hidden" name="tTitle" value="Title" />
	<input type="submit" value="Сохранить настройки" />
</form>

$("#settingsFrm").on("submit", function(eo){
	var $that = $(this);
	var $formData = new FormData($that.get(0));
	alert($that.attr("method"));
	$.ajax({
		url: $that.attr("action"),
		type: $that.attr("method"),
		contentType: "application/x-www-form-urlencoded",
		processData: true,
		data: $formData,
		dataType: "text", //"json",
		success: function(data) {
			alert(data);
		},
		error: function(xhr, textStatus, errorThrown) {
			alert("Ошибка!" + "\n" + xhr + "\n" + xhr.status);// + "\n" + xhr.responseText);
		}
	});
	eo.preventDefault();
});

<?
	if(!empty($_POST[tHeaderText]))
		echo $_POST[tHeaderText];
	else
		echo "Ошибка";
	exit;
?>

$("#settingsFrm").on("submit", function(eo){
	var $that = $(this);
	var $formData = new FormData($that.get(0));
	alert($that.attr("method"));
	$.ajax({
		url: $that.attr("action"),
		type: $that.attr("method"),
		contentType: false,
		processData: false,
		data: $formData,
		dataType: "text", //"json",
		success: function(data) {
			alert(data);
		},
		error: function(xhr, textStatus, errorThrown) {
			alert("Ошибка!" + "\n" + xhr + "\n" + xhr.status);// + "\n" + xhr.responseText);
		}
	});
	eo.preventDefault();
});