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-====== Programming the Wattmon ======
-Programming and scripting will be used interchangeably throughout the document.
-Wattmon is built on a scripting language that is syntactically identical to PHP - we call it uPHP for Micro-PHP.  It has a small but powerful subset of the functions and features found in the PHP language.
-===== Why uPHP? =====
-First perhaps it would be good to explain a bit about how and why we chose PHP.  The goal of Wattmon is to provide a highly flexible platform that can be customized for pretty much any application imaginable keeping in mind very low memory availability.  It became clear that a scripting language would be required to implement this, since having custom firmwares for various applications would be very tedious.  The question then became: what would be the *best* scripting language that is well known today and can be deployed on a microcontroller with such limited resource?  The choices are actually very small.  Most modern scripting languages require quite a bit of RAM.  So, we decided to roll our own scripting language from scratch and base it off a well known language.
-The Wattmon interface is primarily browser based, and generates HTML pages on the fly from uPHP scripts.  The methodology of HTML-PHP integration is well understood by most programmers and hence it allows you to become more productive quickly.
-==== Challenges ====
-The biggest challenge with the scripting language is its memory limitation.  The WattmonPRO and MINI processor both have a total of 128kB (yes, kilobytes!) of RAM available to run a multitasking OS with a TCP/IP and USB stack, modbus polling engine, scheduler and more.  During normal operation scripts have a maximum of about 30 kB of memory for variables, which means that as a programmer you need to be very concious of memory allocation.  We have introduced some special non-PHP compatible variable types to help with this.  The [[wiki:indexed_array|indexed_array()]] function lets you create arrays of a very specific type (int, byte, etc) which will reduce the amount of resources compared to hash arrays created with the [[wiki:array|array()]] function.
-==== Benefits ====
-Having a scripting language that lets you modify and edit your program remotely is a very powerful thing.  It lets you provide remote support to your clients and fix issues without needing to visit the site, and also makes your applications future-proof as you can at any time update the code base and integrate new features or protocols.
-[[wiki:uPHP Language Basics|Language Basics]]
-[[uphp:functions:uphp_function_reference|uPHP Function Reference]]

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