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# exif_imagetype

(PHP 4 >= 4.3.0, PHP 5)

exif_imagetype -- Determine the type of an image

## Description

int exif_imagetype ( string filename)

exif_imagetype() reads the first bytes of an image and checks its signature.

> 備注: Support for JPC, JP2, JPX, JB2, XBM, and WBMP became available in PHP 4.3.2. Support for SWC as of PHP 4.3.0.

This function can be used to avoid calls to other exif functions with unsupported file types or in conjunction with $_SERVER['HTTP_ACCEPT'] to check whether or not the viewer is able to see a specific image in the browser.

## 預先定義常數

The following constants are defined and represent possible exif_imagetype() return values:

表格 1.Imagetype Constants

Value | Constant
--- | ---
1 | `IMAGETYPE_GIF`
2 | `IMAGETYPE_JPEG`
3 | `IMAGETYPE_PNG`
4 | `IMAGETYPE_SWF`
5 | `IMAGETYPE_PSD`
6 | `IMAGETYPE_BMP`
7 | `IMAGETYPE_TIFF_II` (intel byte order)
8 | `IMAGETYPE_TIFF_MM` (motorola byte order)
9 | `IMAGETYPE_JPC`
10 | `IMAGETYPE_JP2`
11 | `IMAGETYPE_JPX`
12 | `IMAGETYPE_JB2`
13 | `IMAGETYPE_SWC`
14 | `IMAGETYPE_IFF`
15 | `IMAGETYPE_WBMP`
16 | `IMAGETYPE_XBM`

## Return values

When a correct signature is found the appropriate constant value will be returned otherwise the return value is `FALSE`. The return value is the same value that getimagesize() returns in index 2 but this function is much faster.

## 範例

示範 1.exif_imagetype() example
`<?php if (exif_imagetype("image.gif") != IMAGETYPE_GIF) { echo "The picture is not a gif"; } ?>`

## 參考

getimagesize()

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