If you run out of memory in Linux, you can create a file to hold additional memory using these commands:
/bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=1024
/sbin/mkswap /var/swap.1
/sbin/swapon /var/swap.1
/sbin/mkswap /var/swap.1
/sbin/swapon /var/swap.1
This creates a 1GB file (you can modify the "count" param) and activates it as additional swap memory.
Final thoughts
I'm not even going to comment on where this piece of information came from, but man, the PHP world...