finfo_open()

finfo::__construct

(PHP >= 5.3.0, PECL fileinfo >= 0.1.0)

创建一个 fileinfo 资源

说明

过程化风格
finfo_open([int $options= FILEINFO_NONE[,string $magic_file= NULL]]): resource

面向对象风格（构造器）：

publicfinfo::__construct([int $options= FILEINFO_NONE[,string $magic_file= NULL]])

本函数打开一个魔数数据库并且返回它的资源。

参数

$options

一个Fileinfo 常量或多个Fileinfo 常量进行逻辑或运算。

$magic_file

魔数数据库文件名称，通常是/path/to/magic.mime。如果未指定，则使用MAGIC环境变量。如果未指定此环境变量，则使用 PHP 绑定的魔数数据库。

传入NULL或者空字符串，等同于使用默认值。

返回值

（仅适用于过程化风格）如果成功则返回一个表示魔数数据库的资源，或者在失败时返回FALSE。

注释

Warning
在 PHP 5.3.11 和 5.4.1 中预期的魔数数据库格式发生了变动，所以，内置的魔数数据库被更新。如果使用了外部魔数数据库，可能会由于格式不同导致读取失败。同时，一些 mime 类型的文字表示也发生了变化，例如，PHP 文件的 mime 类型由“"PHP script text”变为“PHP script, ASCII text”。

Note:
通常来说，使用 PHP 绑定的魔数数据库（设置$magic_file参数为空，不设置MAGIC环境变量）是最好的选择，除非你确实需要一个自定义的魔数数据库。

范例

面向对象风格

<?php
$finfo = new finfo(FILEINFO_MIME, "/usr/share/misc/magic"); // 返回 mime 类型
/* get mime-type for a specific file */
$filename = "/usr/local/something.txt";
echo $finfo->file($filename);
?>

过程化风格

<?php
$finfo = finfo_open(FILEINFO_MIME, "/usr/share/misc/magic"); // 返回 mime 类型
if (!$finfo) {
    echo "Opening fileinfo database failed";
    exit();
}
/* 获取指定文件的 mime 类型 */
$filename = "/usr/local/something.txt";
echo finfo_file($finfo, $filename);
/* 关闭资源 */
finfo_close($finfo);
?>

以上例程会输出：

text/plain; charset=us-ascii

参见

finfo_close()关闭 fileinfo 资源

For most common image files:
<?php
function minimime($fname) {
  $fh=fopen($fname,'rb');
  if ($fh) { 
    $bytes6=fread($fh,6);
    fclose($fh); 
    if ($bytes6===false) return false;
    if (substr($bytes6,0,3)=="\xff\xd8\xff") return 'image/jpeg';
    if ($bytes6=="\x89PNG\x0d\x0a") return 'image/png';
    if ($bytes6=="GIF87a" || $bytes6=="GIF89a") return 'image/gif';
    return 'application/octet-stream';
  }
  return false;
}
?>

I am running Windows 7 with Apache. It took hours to figure out why it was not working.
First, enable the php_fileinfo.dll extension in you php.ini. You'll also need the four magic files that are found in the following library:
http://sourceforge.net/projects/gnuwin32/files/file/4.23/file-4.23-bin.zip/download
An environment variable or a direct path to the file named "magic" is necessary, without any extension. 
Then, make sure that xdebug is either turned off or set the ini error_reporting to not display notices or warnings for the script.
Hope this saves someone a few hours of frustration!

On my Debian squeeze system, the path needed is like :
<?php 
 $finfo = new finfo(FILEINFO_MIME, "/usr/share/misc/magic.mgc");
?>

It seems there is quite some inconsistency in distributions and loading of magic files.
On Archlinux, the file is located here:
/usr/share/misc/file/magic.mgc
But this:
<?php
$fi = new finfo(FILEINFO_MIME, '/usr/share/misc/file/magic');
$fi->file('/tmp/fubar.txt');
?>
Actually segfaults, where if I type the full name (including the file extension:)
<?php
$fi = new finfo(FILEINFO_MIME, '/usr/share/misc/file/magic.mgc'); // added ".mgc"
$fi->file('/tmp/fubar.txt');
?>
It works as expected, so I guess something goes wrong with "A .mime and/or .mgc suffix is added if needed."

Platform: WinXP-SP2, PHP5.2.5, MySQL 5.0, Apache 2.2.8
After reading former notes, I wasn't able to load my magic database: 'magic.mime' file (donwloaded from GnuWin32 project, zipped with the binary files v4.21). I always got an invalid $finfo object or finfo_open(...) returned FALSE.
In order to be able to load the 'magic.mime' file, Fileinfo library (bundled in PHP5.2.5) also requires 'magic' file.
For example:
1. Database:
 c:\php\magic.mime
 c:\php\magic
2. PHP Code:
<?php
 $filname = 'c:\php\php.ini';
 $finfo = new finfo(FILEINFO_MIME, 'c:\php\magic');
 if (!$finfo) return false;
 echo $finfo->file($filename);
?>
For further info see: http://pecl.php.net/bugs/bug.php?id=7555
Pay attention to comments added by 'christophe dot charron dot xul at gmail dot com'
NOTE: Before upgrading to PHP5.2.5, I was working with PHP5.2.1 and it only required 'magic.mime' file.

The current version (1.04) doesnt support a different mime.magic database than the server default.
(the documentation is thus not correct)
Ubuntu default location is '/usr/share/file/magic'. In order for the examples to work all finfo_open() commands must be issued with the extra location accordingly:
<?php
$file = "/path/to/file.jpg";
$handle = finfo_open(FILEINFO_MIME, '/usr/share/file/magic');
$mime_type = finfo_file($handle,$file);
?>

Couldn't get finfo to return the mimetype in the way expected so i made a function to do it with system()
<?php 
function get_mime_type($filepath) {
  ob_start();
  system("file -i -b {$filepath}");
  $output = ob_get_clean();
  $output = explode("; ",$output);
  if ( is_array($output) ) {
    $output = $output[0];
  }
  return $output;
}
?>
hope it works for other people too

Since it costed me some time to find the needed magic database files for Windows, just a hint:
The last release of the GnuWin32 project with both needed files (magic and magic.mime) currently was "file-4.23".
All releases after 4.23 to 4.25-1 did not contain both needed files.
Hope that helps.

Notice FileInfo::__construct() has strange behavior in PHP < 5.3.1 when a 2nd parameter is set explicitly, e.g.;
<?php
$fileInfo = new finfo(FILEINFO_MIME, null);
?>
Expected result:
----------------
object(finfo)#2 (0) { }
Actual result:
--------------
Warning: finfo::finfo(): Failed to load magic database at ''. in *** on line ***
object(finfo)#2 (0) { }
See http://bugs.php.net/bug.php?id=51732

On Windows systems people might find that this always returns "application/x-dpkg".
There are 2 ways of solving this problem:
1. Get the mime-magic database file from GnuWin32 at <http://sourceforge.net/projects/gnuwin32/>
2. You can manually "fix" the mime-magic file by editing it and escaping all lines starting with !, thus changing each one to \!