将图像画布存储到数据库php本地存储

I've been stuck for so many days on this. I'm seeing a lot of the same problem like this, but some of the codes from them won't work on me. To be precise, I'm not using php 5 nor 7. But this is what I've got so far.

(Assuming there are drawings in this canvas) my html:

    <canvas id="displaycanvas" height="400px" width="700px" style="position:absolute; background-image:url('images/canvas_pattern.jpg');background-attachment:fixed;"> </canvas>

    <canvas id="display_text" height="400px" width="700px" style="position:absolute;" > </canvas>

<input type="button" name="btn" id="submitBtn" value="display" class="btn btn-primary" />

And I successfully converted my canvas to image and displays it!

$(function () {
    $("#submitBtn").bind("click", function () {
        var display01 = $('#displaycanvas')[0].toDataURL();
        $("#show_canvas").attr("src", display01);
        $("#show_canvas").show();
    });
});

display part of the image: (works fine)

<img id="show_canvas" name="show_canvas" height="400px" width="700px"/>

now after displaying, I have a button "save" which means to store the image or canvas in my database and it executes at the "submit.php".

but I'm stuck on how am I going to store it in my database... right now I only have a primary key on my "Image_table", not sure what are the right attributes to add.

Thank you in advance!!