$tempfile = tempnam(get_temppath(), "cache");
file_put_contents($tempfile, $img_str);
- $mime = image_type_to_mime_type(exif_imagetype($tempfile));
+
+ // See http://php.net/manual/en/function.exif-imagetype.php#79283
+ if (filesize($tempfile) > 11) {
+ $mime = image_type_to_mime_type(exif_imagetype($tempfile));
+ } else {
+ $mime = false;
+ }
+
unlink($tempfile);
if (substr($mime, 0, 6) == "image/") {