With the exif extension you are able to work with image meta data. For
example, you may use exif functions to read meta data of pictures taken
from digital cameras by working with information stored in the headers of
the JPEG and TIFF images.
Your PHP must be compiled in with --enable-exif.
PHP does not require any additional library for the exif module. Windows
users must also have the mbstring
extension enabled.
To enable exif-support configure PHP with
--enable-exif
Windows users must enable both the php_mbstring.dll
and php_exif.dll DLL's in php.ini. The
php_mbstring.dll DLL must be loaded
before the php_exif.dll DLL so
adjust your php.ini accordingly.
这些函数的行为受到全局配置文件 php.ini 的影响。
Exif supports automatically conversion for Unicode and JIS
character encodings of user comments when module
mbstring
is available. This is done by first decoding the comment
using the specified characterset. The result is then encoded
with another characterset which should match your
HTTP output.
表格 1. Exif configuration options
| Name | Default | Changeable |
|---|
| exif.encode_unicode | "ISO-8859-15" | PHP_INI_ALL |
| exif.decode_unicode_motorola | "UCS-2BE" | PHP_INI_ALL |
| exif.decode_unicode_intel | "UCS-2LE" | PHP_INI_ALL |
| exif.encode_jis | "" | PHP_INI_ALL |
| exif.decode_jis_motorola | "JIS" | PHP_INI_ALL |
| exif.decode_jis_intel | "JIS" | PHP_INI_ALL |
For further details and definition of the PHP_INI_* constants see
ini_set().
以下是该配置选项的简要解释。
- exif.encode_unicode
string
exif.encode_unicode defines the
characterset UNICODE user comments are handled.
This defaults to ISO-8859-15 which should work for
most non Asian countries. The setting can be empty
or must be an encoding supported by mbstring. If it
is empty the current internal encoding of mbstring is
used.
- exif.decode_unicode_motorola
string
exif.decode_unicode_motorola defines
the image internal characterset for Unicode encoded user
comments if image is in motorola byte order (big-endian).
This setting cannot be empty but you can specify a list
of encodings supported by mbstring. The default is UCS-2BE.
- exif.decode_unicode_intel
string
exif.decode_unicode_intel defines
the image internal characterset for Unicode encoded user
comments if image is in intel byte order (little-endian).
This setting cannot be empty but you can specify a list
of encodings supported by mbstring. The default is UCS-2LE.
- exif.encode_jis
string
exif.encode_jis defines the
characterset JIS user comments are handled.
This defaults to an empty value which forces
the functions to use the current internal encoding
of mbstring.
- exif.decode_jis_motorola
string
exif.decode_jis_motorola defines
the image internal characterset for JIS encoded user
comments if image is in motorola byte order (big-endian).
This setting cannot be empty but you can specify a list
of encodings supported by mbstring. The default is JIS.
- exif.decode_jis_intel
string
exif.decode_jis_intel defines
the image internal characterset for JIS encoded user
comments if image is in intel byte order (little-endian).
This setting cannot be empty but you can specify a list
of encodings supported by mbstring. The default is JIS.
由于这些常量是由该扩展模块定义的，因此只有在该扩展模块被编译到 PHP 中，或者在运行时被动态加载后，这些常量才有效。
The exif_imagetype() lists several related built-in
constants.
user_error
