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Exif Functions
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.
The behaviour of these functions is affected by settings in php.ini.
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.
Table 85. Exif configuration options
| Name | Default | Changeable | Changelog |
|---|---|---|---|
| exif.encode_unicode | "ISO-8859-15" | PHP_INI_ALL | Available since PHP 4.3.0. |
| exif.decode_unicode_motorola | "UCS-2BE" | PHP_INI_ALL | Available since PHP 4.3.0. |
| exif.decode_unicode_intel | "UCS-2LE" | PHP_INI_ALL | Available since PHP 4.3.0. |
| exif.encode_jis | "" | PHP_INI_ALL | Available since PHP 4.3.0. |
| exif.decode_jis_motorola | "JIS" | PHP_INI_ALL | Available since PHP 4.3.0. |
| exif.decode_jis_intel | "JIS" | PHP_INI_ALL | Available since PHP 4.3.0. |
For further details and definitions of the
PHP_INI_* constants, see the Appendix I, php.ini directives.
Here's a short explanation of the configuration directives.
- exif.encode_unicode string
exif.encode_unicodedefines 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_motoroladefines 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_inteldefines 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_jisdefines 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_motoroladefines 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_inteldefines 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.
The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.
-
EXIF_USE_MBSTRING(integer)
The exif_imagetype() lists several related built-in constants.
Table of Contents
- exif_imagetype — Determine the type of an image
- exif_read_data — Reads the EXIF headers from JPEG or TIFF
- exif_tagname — Get the header name for an index
- exif_thumbnail — Retrieve the embedded thumbnail of a TIFF or JPEG image
- read_exif_data — Alias of exif_read_data()