Detecting image type from base64 string in PHP

FileInfo can do that for you:

$encoded_string = "....";$imgdata = base64_decode($encoded_string);$f = finfo_open();$mime_type = finfo_buffer($f, $imgdata, FILEINFO_MIME_TYPE);

If you dont want to use these functions because of their dependencies you can use the first bytes of the data:

function getBytesFromHexString($hexdata){  for($count = 0; $count < strlen($hexdata); $count+=2)    $bytes[] = chr(hexdec(substr($hexdata, $count, 2)));  return implode($bytes);}function getImageMimeType($imagedata){  $imagemimetypes = array(     "jpeg" => "FFD8",     "png" => "89504E470D0A1A0A",     "gif" => "474946",    "bmp" => "424D",     "tiff" => "4949",    "tiff" => "4D4D"  );  foreach ($imagemimetypes as $mime => $hexbytes)  {    $bytes = getBytesFromHexString($hexbytes);    if (substr($imagedata, 0, strlen($bytes)) == $bytes)      return $mime;  }  return NULL;}$encoded_string = "....";$imgdata = base64_decode($encoded_string);$mimetype = getImageMimeType($imgdata);

The solution given by @Marc B is the best one for me (if our php version is > 5.3.0 otherwise we can use the solution given by @Aaron Murgatroyd).

I would like to give a little addition to this solution.

To get the image type you can do it like this :

$split = explode( '/', $mime_type );$type = $split[1]; 

In fact, (if you don't know it) the mime type for images is : image/type and type can be png or gif or jpeg or ...

Hope that can help someone and thanks to @Marc B for his solution.

For an exhaustive list of mime type you can look here :

• http://www.sitepoint.com/web-foundations/mime-types-complete-list/