exif_imagetype

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

exif_imagetype判断一个图像的类型

说明

exif_imagetype ( string $filename ) : int

exif_imagetype() 读取一个图像的第一个字节并检查其签名。

本函数可用来避免调用其它 exif 函数用到了不支持的文件类型上或和 $_SERVER['HTTP_ACCEPT'] 结合使用来检查浏览器是否可以显示某个指定的图像。

参数

filename
被检查的图像文件名。

返回值

如果发现了恰当的签名则返回一个对应的常量,否则返回 false。返回值和 getimagesize() 返回的数组中的索引 2 的值是一样的,但本函数快得多。

更新日志

版本 说明
4.3.2 支持 JPCJP2JPXJB2XBM 以及 WBMP
4.3.0 支持 SWC

预定义常量

定义有以下常量,并代表了 exif_imagetype() 可能的返回值:

图像类型常量
常量
1 IMAGETYPE_GIF
2 IMAGETYPE_JPEG
3 IMAGETYPE_PNG
4 IMAGETYPE_SWF
5 IMAGETYPE_PSD
6 IMAGETYPE_BMP
7 IMAGETYPE_TIFF_II(Intel 字节顺序)
8 IMAGETYPE_TIFF_MM(Motorola 字节顺序)
9 IMAGETYPE_JPC
10 IMAGETYPE_JP2
11 IMAGETYPE_JPX
12 IMAGETYPE_JB2
13 IMAGETYPE_SWC
14 IMAGETYPE_IFF
15 IMAGETYPE_WBMP
16 IMAGETYPE_XBM

范例

Example #1 exif_imagetype() 例子

<?php

if (exif_imagetype("image.gif") != IMAGETYPE_GIF) {
    echo 
"The picture is not a gif";
}

?>

参见

User Contributed Notes

vuatintac at yahoo dot com 01-Apr-2015 05:32
to checking file is image, I used this:

function is_image($path)
{
    $a = getimagesize($path);
    $image_type = $a[2];

    if(in_array($image_type , array(IMAGETYPE_GIF , IMAGETYPE_JPEG ,IMAGETYPE_PNG , IMAGETYPE_BMP)))
    {
        return true;
    }
    return false;
}
christophe dot tournayre at univ*bpclermont dot Fr 18-Sep-2013 09:01
Because I only want to check for jpeg or png from a memory string, this is my 2 functions that are quick and don't have any dependencies :

<?php
 
function is_jpeg(&$pict)
  {
    return (
bin2hex($pict[0]) == 'ff' && bin2hex($pict[1]) == 'd8');
  }

  function
is_png(&$pict)
  {
    return (
bin2hex($pict[0]) == '89' && $pict[1] == 'P' && $pict[2] == 'N' && $pict[3] == 'G');
  }
?>
admin at leonard !spam challis dot com 03-Nov-2010 08:02
Windows 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.dll
extension=php_exif.dll

You can check whether this has worked by calling phpinfo() and searching for exif.
tom dot ghyselinck at telenet dot be 13-Jan-2008 01:36
If 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;
    }
}
Tim 19-Nov-2007 08:40
By 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 small
if (filesize($uploadfile) > 11)
    $mimetype = exif_imagetype($uploadfile);
else
    $mimetype = false;
09-Nov-2006 04:43
Seems 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 type
tom at tomvergote dot be 07-Feb-2004 02:11
libexif can also be used to parse image info out of id3 tags:

exif_read_data("mp3_with_2.4ID3TAGS, '', true, false);
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