通过ajax将2d数组传递给php

I have an 2d array, with name data_forms, now i need to pass this array as object to row.php... how i can do that?

in row.php Im try to print print_r($_POST); and output is undefind, also if i try

print_r(json_decode($_POST)); this will give me Warning: json_decode() expects parameter 1 to be string

$(".saveNewRow").click(function(){
    var number_of_row_and_clmn = parseInt($(".row_count_value").val());
    var data_forms = new Array();
    // all lenght are equal so we used just one 
    var array_2d_length = $('.row-font-style-1 .form-1').length;
    for(var i = 0; i< number_of_row_and_clmn; i++){
        data_forms[i] = new Array();
        if($(".row-font-style-"+i).hasClass("its_div")){
            data_forms[i][0] = "div";
        }else{
            data_forms[i][0] = "tr";
        }
        for(var j = 1; j <= array_2d_length; j++){
           data_forms[i][j] = $(".row-font-style-"+(i+1)+" .field-"+(j-1)).val();
        }
    }
    $.ajax ({ 
        url:"row.php",
        type:"post",
        data:data_forms,
        dataType:JSON,
        statusCode:{
        404:function(){
            $("#output_data").html("page not found!!");
        }},
        success:function (data) {
            $("#output_data").html(data);
        },
        complete:function(){
        }
    });
});

thanks for help

Im found a problem, Im change this data:data_forms to data:{mydata: data_forms} also Im remove dataType:JSON

after im do that, ajax page work fine ... thanks alot for all