$ sudo yum install httpd24 php54 php54-mysql php54-pecl-memcached
$ sudo ln -s /home/isucon/webapp/php/etc/isucon.php.conf.sample /etc/httpd/conf.d/isucon.php.conf
$ sudo service httpd restart
for php54-mysql, set LD_LIBRARY_PATH
LD_LIBRARY_PATH=/usr/lib64/mysql
etc/isucon.php.conf.sample