php PECL mcrypt を入れようとしたときのconfigureで configure: error: mcrypt.h not found. Please reinstall libmcrypt. がでたら
yum install libmcrypt-devel /usr/local/php/bin/phpize ./configure -with-mcrypt=/usr --with-php-config=/usr/local/php/bin/php-config make make install
libmcrypt-develをいれて-with-mcrypt=/usrをつけると良さげです