php 读取文件头判断文件类型的实现代码

<?php $filename = "11.jpg";
//为图片的路径可以用d:/upload/11.jpg等绝对路径
$file = fopen($filename, "rb");
$bin = fread($file, 2); //只读2字节
fclose($file);
$strInfo = @unpack("C2chars", $bin);
$typeCode = intval($strInfo[‘chars1‘].$strInfo[‘chars2‘]);
$fileType = ‘‘;
switch ($typeCode) {
case 7790: $fileType = ‘exe‘; break;
case 7784: $fileType = ‘midi‘; break;
case 8297: $fileType = ‘rar‘; break;
case 255216: $fileType = ‘jpg‘; break;
case 7173: $fileType = ‘gif‘; break;
case 6677: $fileType = ‘bmp‘; break;
case 13780: $fileType = ‘png‘; break;
default: echo‘unknown‘;
}
echo‘这是一个‘.$fileType.‘ file:‘.$typeCode;

?>
//linux下php还有个函数可以判断文件类型
<?php
echo mime_content_type(‘11.gif‘) . "\n";
echo mime_content_type(‘22.php‘);
?>