Description:
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The IMAGETYPE_XXX constant names aren't listed anywhere, or at least the place where they are listed cannot be easily reached from either exif_imagetype() or getimagesize() documentation (the former directs the user to the latter, promising that the constants WILL be listed there, but they aren't). This leaves the programmer to try-and-error whether it's e.g. IMAGETYPE_JPG or IMAGETYPE_JPEG or something else entirely.

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From manual page: http://www.php.net/function.getimagesize#refsect1-function.getimagesize-changelog
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