当前使用的安装包版本：
freetype-2.4.0.tar.bz2
jpegsrc.v9.tar.gz
libpng-1.6.28.tar.gz
1、安装freetype
tar jxvf freetype-2.4.0.tar.bz2
cd freetype-2.4.0
./configure --prefix=/usr/local/freetype
make && make install
2、安装jpegsrc
tar zxvf jpegsrc.v9.tar.gz
cd jpeg-9
./configure --prefix=/usr/local/jpeg && make && make install
mkdir -p /usr/local/jpeg/include \
mkdir -p /usr/local/jpeg/lib \
mkdir -p /usr/local/jpeg/bin \
mkdir -p /usr/local/jpeg/man/man1
3、安装libpng
tar zxvf libpng-1.6.28.tar.gz
cd libpng-1.6.28
./configure --prefix=/usr/local/libpng
make && make install
4、进入PHP安装包里面的ext文件夹，找到gd扩展
cd /home/local/php-5.6.25/ext/gd
/usr/local/php/bin/phpize
./configure --with-php-config=/usr/local/php/bin/php-config --with-jpeg-dir=/usr/local/jpeg --with-png-dir=/usr/local/libpng --with-freetype-dir=/usr/local/freetype
如果出现configure: error: Problem with libpng.(a|so) or libz.(a|so). Please check config.log for more information
换个版本的libpng重新安装就好
make && make install
cp /usr/local/php/lib/php/extensions/no-debug-zts-20131226/gd.so /usr/local/php/extension/gd.so
vim /usr/local/php/etc/php.ini 添加:extension=gd.so
重启服务器，/usr/local/php/bin/php -m 就能看到了