I am using php ssh2_exec to execute a ps aux command on a remote Linux server… The server initiating the connection is Ubuntu 14.04 and the server I am communicating with is Centos 6.6. Both systems are fully updates and I am using the following versions of PHP and Apache on the Ubuntu system: apache2 2.4.7-1ubuntu4.5 libapache2-mod-php5 5.5.9+dfsg-1ubuntu4.11 php5 5.5.9+dfsg-1ubuntu4.11