参照：http://stackoverflow.com/questions/7290958/php-fatal-error-call-to-undefined-function-imagettftext
Just recompile extension gd.so, under folder php/ext/gd
./configure --with-php-config=/usr/local/php5/bin/php-config --with-freetype-dir=/usr/ --enable-gd-native-ttf
fatal error: call to undefined function imagettftext
原文：http://www.cnblogs.com/the-moving-ear/p/4662841.html