That is definitely a memory issue. PHP administration is beyond the purview of DSP, but I do believe that the Bitnami stacks come with a default setting in php.ini of memory_limit = 128M.
If you plan to host a production PHP application like DSP, I recommend researching PHP configuration and tuning your server appropriately for your expected number of users, throughput of data, server hardware, etc. Here is PHP’s documentation on memory_limit:
http://php.net/manual/en/ini.core.php#ini.sect.resource-limits