php扩展文件信息安装在Ubuntu中(15.10）

我尝试在Ubuntu（15.10）中安装php文件信息扩展，但出现错误：

sudo pecl install fileinfo

错误：

WARNING: "pear/Fileinfo" is deprecated in favor of "channel://php-src/ext/fileinfo/in php sources"
WARNING: channel "pear.php.net" has updated its protocols, use "pecl channel-update pear.php.net" to update
downloading Fileinfo-1.0.4.tgz ...
Starting to download Fileinfo-1.0.4.tgz (5,835 bytes)
.....done: 5,835 bytes
3 source files, building
running: phpize
Cannot find config.m4.
Make sure that you run '/usr/bin/phpize' in the top level source directory of the module
If the command failed with 'phpize: not found' then you need to install php5-dev packageYou can do it by running 'apt-get install php5-dev' as a root userERROR: `phpize' failed

然后我尝试了这个命令：

sudo apt-get install php5-dev

输出：

Reading package lists... Done
Building dependency tree       
Reading state information... Done
php5-dev is already the newest version.
The following packages were automatically installed and are no longer required:
  linux-headers-4.2.0-16 linux-headers-4.2.0-16-generic
  linux-image-4.2.0-16-generic linux-image-extra-4.2.0-16-generic
  linux-signed-image-4.2.0-16-generic
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.

如何安装php文件信息扩展？如何启用此扩展？