php 如何判断二进制流的文件类型

<code class="php">$image=file_get_contents($url);
file_put_contents($imagePath, $image);   //将图片流存入服务器图片目录
$type=image_type_to_extension(exif_imagetype($imagePath));   //文件类型</code>

<code class="php">$image=file_get_contents($url);
file_put_contents($imagePath, $image);   //将图片流存入服务器图片目录
$type=image_type_to_extension(exif_imagetype($imagePath));   //文件类型</code>

<code>$image = file_get_contents($url);

echo check_image_type($image);

function check_image_type($image)
{
    $bits = array(
        'JPEG' => "\xFF\xD8\xFF",
        'GIF' => "GIF",
        'PNG' => "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a",
        'BMP' => 'BM',
    );
    foreach ($bits as $type => $bit) {
        if (substr($image, 0, strlen($bit)) === $bit) {
            return $type;
        }
    }
    return 'UNKNOWN IMAGE TYPE';
}</code>

<code>$finfo = new finfo(FILEINFO_MIME_TYPE);
var_dump($finfo->file('t.jpg')); // ==> image/jpeg</code>