Office of Digital Humanities

DigHT 310
Server-side LiveCode Scripting – lesson notes

The LiveCode server-side scripting technology allows you to mix LiveCode code with HTML content on the same web page, in much the same way as PHP, the most widely-used server-side scripting language. The advantage for LiveCode developers is that they can use the very same language they use to develop desktop applications to create dynamic web pages. While the language is the same there are a few differences and additions to LiveCode as used in server-side scripting, compared to the way it is used in developing stacks. Here is a summary of the main differences:

• The whole point of LiveCode scripting is to create HTML output. The power of LiveCode Server scripting is that the HTML output—the content the end user will see—can be dynamic, changing according to conditions or user inputs.
• In the LiveCode IDE a put command without a destination container, such as put "Hello World", is directed to the message box. There is no message box in the server-side environment; instead a put without a destination is returned to the client or web browser that called the URL. In a web browser it is displayed as part of the html output.
• In the server scripting environment there are no objects; i.e., no stacks, cards, fields, buttons, images, etc. This has several implications:
• there are no properties to set, other than global properties like the defaultFolder and the itemDelimiter;
• there is no way to set custom properties;
• the only containers available to put data into are variables and files on the server.
• In LiveCode Server scripting you can use handlers and functions exactly as in LiveCode stacks. The handlers can be defined anywhere in the .lc document.
• Due to the unique nature of the web server environment, there are a handful of LiveCode Server-specific vocabulary elements:
• include command – You can access library stacks in the LiveCode Server environment just as you can in LiveCode itself. You can also use the include command you can reference other .lc files containing frequently used handlers and use their scripts as if they were part of the current file. For example, say we have a file containing frequently used handlers called "mylibrary.lc" in the same folder as your current .lc file. It could contain our old friend the q() function, which returns a string with double quotes around it. We could do this in our .lc file:

     include "mylibrary.lc"
     put "<p>" & q("Hello World") & "</p>"

• $_GET and $_POST array variables – When a form on a web page is submitted to the .lc script, or a URL with a query string is requested, the LiveCode Server engine will attempt to parse this data into structured arrays. For a query string, or a form 'GET' method, this information will placed in the $_GET array. For a form 'POST' method, this information will be placed in the $_POST array. In both cases the conversion to an array is the same. The incoming data is a set of key=value pairs. The key determines which element of the array the value gets put in.
• $_SERVER array variable - contains lots of information about the client and server environments. See an example here.
• the errormode property
  set the errormode to "inline" - displays LiveCode scripting errors in the web page; good for debugging (remember to comment out before you go final on your page.)