<?php  
$filename = "D:/296.mid";  
$file = fopen($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:  
$fileType = 'png';  
break;  
default:  
echo 'unknown';  
}  
echo 'this is a(an) '.$fileType.' file:'.$typeCode;  
?>

<?php
echo mime_content_type('php.gif') . "\n";
echo mime_content_type('test.php');
?>