I've created an Amazon Linux AMI 2013.09.02 server and installed the following:
yum install php55 php55-mbstring php55-soap php55-gd php55-mcrypt php55-pdo httpd24
Apache and PHP work fine. But I need pdo_mysql.so for a legacy version of Doctrine (1.x). I cannot find out how to get pdo_mysql.so onto this system. That file is not within the /user/lib64/php/5.5/modules/ folder.