PHP : binary image data, checking the image type

I can see that most of you didn't understand the question :) (question was how to validate binary data in buffer, not a file on disk).

I had same problem, and resolved it with:

$finfo = new finfo(FILEINFO_MIME_TYPE);
$mimeType = $finfo->buffer($rawImage);

The bits start with:

$JPEG = "\xFF\xD8\xFF"
$GIF  = "GIF"
$PNG  = "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a"
$BMP  = "BM"
$PSD  = "8BPS"
$SWF  = "FWS"

The other ones I wouldn't know right now, but the big 3 (jpeg,gif,png) usually cover 99%. So, compare the first bytes to those string, and you have your answer.

Are the files being uploaded or are they already on the file system?

Try using mime_content_type() to get the file's MIME format.

Here's an implementation of the function as described by Wrikken

function getImgType($filename) {
    $handle = @fopen($filename, 'r');
    if (!$handle)
        throw new Exception('File Open Error');

    $types = array('jpeg' => "\xFF\xD8\xFF", 'gif' => 'GIF', 'png' => "\x89\x50\x4e\x47\x0d\x0a", 'bmp' => 'BM', 'psd' => '8BPS', 'swf' => 'FWS');
    $bytes = fgets($handle, 8);
    $found = 'other';

    foreach ($types as $type => $header) {
        if (strpos($bytes, $header) === 0) {
            $found = $type;
            break;
        }
    }
    fclose($handle);
    return $found;
}