I'm displaying images from outside my web root, like this:
header('Content-type:image/png');
readfile($fullpath);
The content-type: image/png is what confuses me.
Someone else helped me out with this code, but I noticed that not all images are PNG. Many are jpg or gif.
And still they are displayed successfully.
does anyone know why?
The best solution would be to read in the file, then decide which kind of image it is and send out the appropriate header
$filename = basename($file);
$file_extension = strtolower(substr(strrchr($filename,"."),1));
switch( $file_extension ) {
case "gif": $ctype="image/gif"; break;
case "png": $ctype="image/png"; break;
case "jpeg":
case "jpg": $ctype="image/jpeg"; break;
case "svg": $ctype="image/svg+xml"; break;
default:
}
header('Content-type: ' . $ctype);
(Note: the correct content-type for JPG files is image/jpeg)
case "svg": $ctype="image/svg+xml"; break;.There is a better way to determine the type of an image. with exif_imagetype
If you use this function, you can tell the image's real extension.
with this function, the filename's extension is completely irrelevant, which is good.
function setHeaderContentType(string $filePath): void
{
$numberToContentTypeMap = [
'1' => 'image/gif',
'2' => 'image/jpeg',
'3' => 'image/png',
'6' => 'image/bmp',
'17' => 'image/ico'
];
$contentType = $numberToContentTypeMap[exif_imagetype($filePath)] ?? null;
if ($contentType === null) {
throw new Exception('Unable to determine content type of file.');
}
header("Content-type: $contentType");
}
You can add more types to the map from this link.
Hope it helps.
Browsers make their best guess with the data they receive. This works for markup (which Websites often get wrong) and other media content. A program that receives a file can often figure out what its received regardless of the MIME content type it's been told.
This isn't something you should rely on however. It's recommended you always use the correct MIME content.
Though weirdly named, you can use the getimagesize() function. This will also give you mime information:
Array
(
[0] => 295 // width
[1] => 295 // height
[2] => 3 // http://php.net/manual/en/image.constants.php
[3] => width="295" height="295" // width and height as attributes
[bits] => 8
[mime] => image/png
)
Browsers can often tell the image type by sniffing out the meta information of the image. Also, there should be a space in that header:
header('Content-type: image/png');
if you know the file name, but don't know the file extention you can use this function:
public function showImage($name)
{
$types = [
'gif'=> 'image/gif',
'png'=> 'image/png',
'jpeg'=> 'image/jpeg',
'jpg'=> 'image/jpeg',
];
$root_path = '/var/www/my_app'; //use your framework to get this properly ..
foreach($types as $type=>$meta){
if(file_exists($root_path .'/uploads/'.$name .'.'. $type)){
header('Content-type: ' . $meta);
readfile($root_path .'/uploads/'.$name .'.'. $type);
return;
}
}
}
Note: the correct content-type for JPG files is image/jpeg.
A simpler way to handle any image type would be:
header("Content-Type: ".image_type_to_mime_type(exif_imagetype($fullpath)));
image_type_to_mime_type has been in php since at least 5.0, I don't know why it was never suggested.
