I'd normally agree, but "embedded device" in this situation means "network router" (which are reasonably powerful computers in their own rights), and the application is not mission critical with hard deadlines and strict memory requirements, but just a web interface that is rarely active and can take as long as it wants running in the background. It doesn't seem unreasonable to me to set aside some portion of memory for the web interface, give the PH7 process low priority, and hire some PHP web devs that actually know what they're doing to make the interface for them. More sense than letting the firmware developers hack something together in C anyway.