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Asked: 2026-05-28T16:33:50+00:00

I have a class with several functions that can render images. // render.php class

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I have a class with several functions that can render images. 

// render.php
class Render {
   public function Render($some_arguments) {
      ...
      header("Content-Type: image/png");
        $im = @imagecreate(110, 20)
            or die("Cannot Initialize new GD image stream");
        $background_color = imagecolorallocate($im, 0, 0, 0);
        $text_color = imagecolorallocate($im, 233, 14, 91);
        imagestring($im, 1, 5, 5,  "A Simple Text String", $text_color);
        imagepng($im);
        return "data:image/png;base64,".base64_encode($im);
   }
}

Then I have my php file that contains the html code and where I would like to output the image within an < img> tag:

// index.php
include("render.php");
$render = new Render();
echo "<htlm><head></head><body>";
echo "<img src=\"".$render->Render(1)."\" />";
echo "</body></html>";

When I run index.php in my browser I just get a blank screen.

Can´t I use a function call as an image source? I know I can use a php file as source, like < img src="render_image.php" />, but then I cannot send any arguments in an object oriented manner (I know I can use $_GET to retrieve arguments), but I would like to do it with a nice object oriented written code.

So, is there any way to use a function call as a source of a html tag?

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1 Answer

  1. Editorial Team

    You’ll have to split it:

    Render(...) will write a temporary file (with a randomized name), that is accessible from the web for some time.

    A new method Output() will return the randomized name mentioned above.

    You then call Render() before outputting the HTML and embed the URL using Output().

    As an alternative, you could use some file or database to exchange the parameters, essentially some method Prepare(...)? writing the params to the file or database, and Render() reading those and placing the file again etc.

    As yet another alternative (without writing to the file system): You could implement include the image data using a data: uri, but the image size will be limited depending on the browser used and you can’t cache the data this way (i.e. you have to send it all the time).

    Depending on what you’re trying to achieve, you might have luck embedding a SVG image as well. This would offer the huge advantage of being in-place while still using less bandwith, being scalable, etc. Downside is, this is only supported in newest browsers (similar to data:) but there are no size restrictions.

    Edit: Using the base64/embedded approach it get’s a bit more tricky resulting in something like this (untested, but should work):

    ob_start(); // buffers future output
imagepng($img); // writes to output/buffer
$b64 = base64_encode(ob_get_contents()); // returns output
ob_end_clean(); // clears buffered output
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