我是在CentOS6.5安装php5.5.28这个版本，PHP编译代码如下：
安装过程不再赘述。因为在编译安装时没有把mcrypt这个扩展编译进去，所以在phpmyadmin里有这样一句提示：
缺少 mcrypt 扩展。请检查 PHP 配置。
另外在独立安装mycrypt扩展时，报错：
configure: error: mcrypt.h not found. Please reinstall libmcrypt.
现在把mcrypt扩展安装过程贴出来，希望对遇到此类问题的朋友有帮助：
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下载libmcrypt-2.5.8.tar.gz
tar zxvf libmcrypt-2.5.8.tar.gz
cd libmcrypt-2.5.8
./configure --prefix=/usr/local/libmcrypt
make install
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下载mhash-0.9.9.9.tar.gz
tar zxvf mhash-0.9.9.9
cd mhash-0.9.9.9
./configrue --prefix=/usr/local/mhash
make
make install
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tar zxvf mcrypt-2.6.8.tar.gz
cd mcrypt-2.6.8
export LD_LIBRARY_PATH=/usr/local/libmcrypt/lib:/usr/local/mhash/lib
export LDFLAGS="-L/usr/local/mhash/lib -I/usr/local/mhash/include/"
export CFLAGS="-I/usr/local/mhash/include/"
./configure --prefix=/usr/local/mcrypt --with-libmcrypt-prefix=/usr/local/libmcrypt
make
make install
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cd /usr/local/src/develop/php-5.5.28/ext/mcrypt
/usr/local/php/bin/phpize
--with-mcrypt=/usr/local/libmcrypt
make
make install
因为我在php.ini设置extension_dir = /usr/local/php/extensions,
所以需要执行：
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