access the data passed through FormData on clicking submit button - php

Question

I have a form with several input fields including file inputs.I am using jquery validate plugin.I need to submit the form using ajax.
HTML:
<form method="post" name="addstudent" id="registrationform" enctype="multipart/form-data">
some fields
<input type="submit" id="buttontext"
class="student_registrationform_button" value="submit" />
Jquery:
$('#buttontext').click(function(){
$("#registrationform").validate({
invalidHandler: function(event, validator) {
//some code
},
submitHandler: function(form){
formdata = false;
if (window.FormData) {
formdata = new FormData();
}
var i = 0, len = $(".file").length, img, reader, file;
$('.file').each(function() { var file = this.files[0];
if (window.FileReader) {
reader = new FileReader();
reader.readAsDataURL(file);
}
if (formdata) {
formdata.append("file", file);
}
});
$.ajax({
url: "process.php",
type: 'POST',
//data: $(this).serialize(),
data: formdata,
cache: false,
contentType: false,
processData: false,
success:function(data){ //alert(data);
console.log(data);return false;
}
Process.php
When I check echo 'action:'.var_dump($_POST); ,its showing null string

Answer 1

(function($) {
$.fn.serializefiles = function() {
var obj = $(this);
var form_data = new FormData(this[0]);
$.each($(obj).find('input[type="file[]"]'), function(i, tag) {
$.each($(tag)[0].files, function(i, file) {
form_data.append(tag.name, file);
});
});
var params = $(obj).serializeArray();
$.each(params, function (i, val) {
form_data.append(val.name, val.value);
});
return form_data;
};
})(jQuery);
var form_id = $('#registrationform');
$.ajax({
type: "POST",
url: "process.php",
data: form_id.serializefiles(),
cache: false,
processData: false,
contentType: false,
success: function (response) {
console.log(data);return false;
}
});

Answer 2

Try this simple function:
submitHandler: function(form){
formdata = new FormData(form);
$.ajax({
url: "process.php",
type: 'POST',
//data: $(this).serialize(),
data: formdata,
cache: false,
contentType: false,
processData: false,
success:function(data){ //alert(data);
console.log(data);return false;
}