SVG from PHP script is not working in img src - php

Question

I'm trying to open SVG file first in PHP and then return this data:
$file = dirname(__FILE__) . $_GET["file"] . ".svg";
if (!file_exists($file)) {
$file = dirname(__FILE__) . $_GET["file"] . ".png";
if (!file_exists($file)) {
throw new NotFoundHttpException();
} else
header('Content-Type: image/png');
} else
header('Content-Type: image/svg+xml');
$content = file_get_contents($file);
return $content;
And in HTML:
<img src="script.php?file=someimage">
Problem is that its not showing SVG images in the tag. It works, if I set script.php?file=someimage to the URL string of my browser, but not inside the tag. PNG works fine. If i set just
<img src="someimage.svg">
it also works perfect.
embed and object tags works, but I need img.
UPDATE:
The problem was in Yii2, I send headers wrong way. In some reason it works for PNG, but not for SVG.
It should be done like that:
Yii::$app->response->format = \yii\web\Response::FORMAT_RAW;
Yii::$app->response->headers->add('Content-Type', 'image/svg+xml');

Answer 1

Looks like you forgot the /. Try replacing these lines where appropriate:
$file = dirname(__FILE__) . '/' . $_GET["file"] . ".svg";
// ...
$file = dirname(__FILE__) '/' . $_GET["file"] . ".png";
dirname() gives back a string without a trailing slash, so it was trying to open /path/to/scriptdirsomefile.svg.
Security
Also, I noticed that your script can be made to do bad things, such as exposing arbitrary files on the server. You can prevent a lot of exploits by doing some basic sanitizing of $_GET['file'] before starting:
$_GET['file'] = preg_replace('#/#', '_', $_GET['file']);

Answer 2

Change return $content; to echo $content;
So if the image files are on the same directory, it will be:
<?php
$file = $_GET["file"] . ".svg";
if (!file_exists($file)) {
$file = $_GET["file"] . ".png";
if (!file_exists($file)) {
throw new NotFoundHttpException();
} else
header('Content-Type: image/png');
} else
header('Content-Type: image/svg+xml');
$content = file_get_contents($file);
echo $content;
?>
Working example #1 (showing svg):
http://www.createchhk.com/SOanswers/subc/index.php
Working example #2 (showing png):
http://www.createchhk.com/SOanswers/subc/index2.php