finfo_open()

finfo::__construct

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

创建一个 fileinfo 资源

说明

面向对象风格（构造器）：

本函数打开一个魔数数据库并且返回它的资源。

参数

一个Fileinfo 常量或多个Fileinfo 常量进行逻辑或运算。

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

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”。

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

过程化风格

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: 

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 : 

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:

Actually segfaults, where if I type the full name (including the file extension:)

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:

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: 

Couldn't get finfo to return the mimetype in the way expected so i made a function to do it with system()

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 
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 
2. You can manually "fix" the mime-magic file by editing it and escaping all lines starting with !, thus changing each one to \!