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# exif_read_data

(PHP 4 >= 4.2.0, PHP 5)

exif_read_data -- Reads the EXIF headers from JPEG or TIFF

## Description

array exif_read_data ( string filename [, string sections [, bool arrays [, bool thumbnail]]])

The exif_read_data() function reads the EXIF headers from a JPEG or TIFF image file. This way you can read meta data generated by digital cameras.

filename is the name of the file to read. This cannot be a URL.

sections is a comma separated list of sections that need to be present in file to produce a result array. If none of the requested sections could be found the return value is `FALSE`.

FILE | FileName, FileSize, FileDateTime, SectionsFound
COMPUTED | html, Width, Height, IsColor and some more if available.
ANY_TAG | Any information that has a Tag e.g. IFD0, EXIF, ...
IFD0 | All tagged data of IFD0. In normal imagefiles this contains image size and so forth.
THUMBNAIL | A file is supposed to contain a thumbnail if it has a second IFD. All tagged information about the embedded thumbnail is stored in this section.
COMMENT | Comment headers of JPEG images.
EXIF | The EXIF section is a sub section of IFD0. It contains more detailed information about an image. Most of these entries are digital camera related.

arrays specifies whether or not each section becomes an array. The sections COMPUTED, THUMBNAIL and COMMENT always become arrays as they may contain values whose names are conflict with other sections.

thumbnail whether or not to read the thumbnail itself and not only its tagged data.

> 備注: Exif headers tend to be present in JPEG/TIFF images generated by digital cameras, but unfortunately each digital camera maker has a different idea of how to actually tag their images, so you can't always rely on a specific Exif header being present.

> Windows ME/XP both can wipe the Exif headers when connecting to a camera. More information available at http://www.canon-asia.com/products/digital_cameras/winxp_problems.html.

> 備注: If the image contains any IFD0 data then COMPUTED contains the entry ByteOrderMotorola which is 0 for little-endian (intel) and 1 for big-endian (motorola) byte order. This was added in PHP 4.3.0.

> When an Exif header contains a Copyright note this itself can contain two values. As the solution is inconsistent in the Exif 2.10 standard the COMPUTED section will return both entries Copyright.Photographer and Copyright.Editor while the IFD0 sections contains the byte array with the NULL character that splits both entries. Or just the first entry if the datatype was wrong (normal behaviour of Exif). The COMPUTED will contain also an entry Copyright Which is either the original copyright string or it is a comma separated list of photo and editor copyright.

> 備注: The tag UserComment has the same problem as the Copyright tag. It can store two values first the encoding used and second the value itself. If so the IFD section only contains the encoding or a byte array. The COMPUTED section will store both in the entries UserCommentEncoding and UserComment. The entry UserComment is available in both cases so it should be used in preference to the value in IFD0 section.

> If the user comment uses Unicode or JIS encoding and the module mbstring is available this encoding will automatically changed according to the exif ini settings in the `php.ini`. This was added in PHP 4.3.0.

> 備注: Height and Width are computed the same way getimagesize() does so their values must not be part of any header returned. Also html is a height/width text string to be used inside normal HTML.

> 備注: Starting from PHP 4.3.0, the function can read all embedded IFD data including arrays (returned as such). Also the size of an embedded thumbnail is returned in THUMBNAIL subarray and the function exif_read_data() can return thumbnails in TIFF format. Also as of PHP 4.3.0 there is no longer a maximum length for returned values (not until memory limit is reached).

Since PHP 4.3,0 user comment can automatically change encoding if PHP was compiled using --enable-mbstring.

## Return values

It returns an associative array where the array indexes are the header names and the array values are the values associated with those headers. If no data can be returned, exif_read_data() will return `FALSE`.

## 範例

示範 1.exif_read_data() example
`<?php echo "test1.jpg:<br />\n"; $exif = exif_read_data('tests/test1.jpg', 'IFD0'); echo $exif===false ? "No header data found.<br />\n" : "Image contains headers<br />"; $exif = exif_read_data('tests/test2.jpg', 0, true); echo "test2.jpg:<br />\n"; foreach ($exif as $key => $section) { foreach ($section as $name => $val) { echo "$key.$name: $val<br />\n"; } } ?>`
The first call fails because the image has no header information.
`test1.jpg: No header data found. test2.jpg: FILE.FileName: test2.jpg FILE.FileDateTime: 1017666176 FILE.FileSize: 1240 FILE.FileType: 2 FILE.SectionsFound: ANY_TAG, IFD0, THUMBNAIL, COMMENT COMPUTED.html: width="1" height="1" COMPUTED.Height: 1 COMPUTED.Width: 1 COMPUTED.IsColor: 1 COMPUTED.ByteOrderMotorola: 1 COMPUTED.UserComment: Exif test image. COMPUTED.UserCommentEncoding: ASCII COMPUTED.Copyright: Photo (c) M.Boerger, Edited by M.Boerger. COMPUTED.Copyright.Photographer: Photo (c) M.Boerger COMPUTED.Copyright.Editor: Edited by M.Boerger. IFD0.Copyright: Photo (c) M.Boerger IFD0.UserComment: ASCII THUMBNAIL.JPEGInterchangeFormat: 134 THUMBNAIL.JPEGInterchangeFormatLength: 523 COMMENT.0: Comment #1. COMMENT.1: Comment #2. COMMENT.2: Comment #3end THUMBNAIL.JPEGInterchangeFormat: 134 THUMBNAIL.Thumbnail.Height: 1 THUMBNAIL.Thumbnail.Height: 1`

## 參考

exif_thumbnail(), and getimagesize().

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