1.问题，项目中上传文件使用插件时，windows上支持函数exif_imagetype（），而在linux上不支持。

2.PHP exif_imagetype的本质

PHP exif_imagetype note #1Windows users: If you get the fatal error "Fatal error:  Call to undefined function exif_imagetype()", and you have enabled php_exif.dll, make sure you enable php_mbstring.dll.  You must put mbstring before exif in the php.ini, i.e.:extension=php_mbstring.dllextension=php_exif.dllYou can check whether this has worked by calling phpinfo() and searching for exif.PHP exif_imagetype note #2If the function exif_imagetype() is not available,you can try the following workaround:if ( ! function_exists( 'exif_imagetype' ) ) {    function exif_imagetype ( $filename ) {        if ( ( list($width, $height, $type, $attr) = getimagesize( $filename ) ) !== false ) {            return $type;        }    return false;    }}PHP exif_imagetype note #3By trial and error, it seems that a file has to be 12 bytes or larger in order to avoid a "Read error!".  Here's a work-around to avoid an error being thrown:// exif_imagetype throws "Read error!" if file is too smallif (filesize($uploadfile) > 11)    $mimetype = exif_imagetype($uploadfile);else    $mimetype = false;PHP exif_imagetype note #4Seems to give a 'Read error' warning if the size of the file is very small (2 bytes). I think this is because it needs a min 3 bytes to determine the file typePHP exif_imagetype note #5libexif can also be used to parse image info out of id3 tags:exif_read_data("mp3_with_2.4ID3TAGS, '', true, false);PHP exif_imagetype note #6After looking for hours, I found a very good source for exif related programs here: http://drewnoakes.com/code/exif/index.htmlIt lists exif specifications (pdf), a few good links to exif related stuff. The best source I have found in my quest to understand exif better for use in php based exif tools.

 

3.解决方案：

 if ( ! function_exists( 'exif_imagetype' ) ) {
             // $currFile = $file['tmp_name'];           list($width, $height, $type2, $attr) = getimagesize($file['tmp_name']);            $type = $type2;           // function exif_imagetype ($currFile) {
             //   if ( ( list($width, $height, $type2, $attr) = getimagesize($currFile) ) !== false ) {
             //       // return $type;           //     $type = $type2;           //   }           //   return false;           // }         }else{
              // $type = exif_imagetype($src);           $type = exif_imagetype($file['tmp_name']);         }