Symptoms
File Manager shows the error:
Invalid backend response.
Data is not JSON.
Cause
The issue is caused by outdated version of PHP installed on Linux File Manager.
Resolution
Update PHP using the following commands:
yum remove php5-cgi
yum install php53 php53-common php53-cli php53-bcmath php53-dba php53-gd php53-imap php53-ldap php53-mbstring php53-mysql php53-odbc php53-pdo php53-pgsql php53-snmp php53-soap php53-xml php53-xmlrpc php53-process