There are a number of options for using PHP with FileMaker. The new custom web publishing feature within FileMaker Server 12 Advanced is substantially faster than the previous versions. So that is probably the first option a person might consider.
Of course, another option is to convert the FileMaker database data, structure, business logic and layouts into a PHP web application running on MySQL. This type of conversion is often done in order to provide improved performance and scalability since there are limitations of 100/200 simultaneous users for either IWP or custom web publishing using PHP.
Most people don't realize it, but there is a wealth of FileMaker metadata available in XML format for performing these types of conversions. This XML info is available either thru copying the layout via the clipboard or reading it from the Database Design Report XML file. I have found the clipboard data to be the most reliable source of this info.
There are tools available to parse in the XML and analyze the database.
It is even possible to automate the PHP conversion using this technique (perform a Google search for "FileMaker to PHP Conversion" for more info).
Each object on a layout is represented in XML, along with style and position info. This info can be used to create form files representing the same look as the original layout. In fact, it can be difficult to see the difference between the web application and the original database if you get all of the object properties implemented. And this is what my customers request, because they don't want to have to retrain their employees. They want the web application to look and work the same as the original desktop application.
I have done a few of these conversions recently into the CakePHP framework. Here a few techniques I used:
Auto-Enter Calculation Fields - Stored calculation fields are calculated and stored within the model saves a record to the database.
Unstored Calculation Fields - Unstored Calculation fields are calculated in real-time within the form controller - but only for fields actually displayed on the form. This prevents unnecessarily calculating these values if they aren't being used on a form, improving performance.
Global Fields - A Global field in FileMaker is used like a global variable in programming languages. It is important to know that each FileMaker user gets there own private copy of global field data. There is no equivalent feature MySQL or other SQL database servers, but this functionality can easily be simulated using SESSION variables. Therefore each web user will still get their own private SESSION data, simulating the same functionality originally present in the FileMaker database. I structure these globals in the model data array as if they were retrieved from the model, meaning that converted scripts and fields on forms can reference them easily. Just before the record gets written into the database, the results are saved into SESSION variables for persistence.
Vector Graphic Objects - FileMaker layouts frequently include rectangles, ovals and line objects. These objects can be replaced with the RafaelJS library, providing high quality resolution independent graphics.
Value Lists - Custom and Field based value lists are implemented in a centralized location within the AppController.php file. Therefore making a change to the definition of the value list within the AppController, succeeds in changing the menu automatically throughout the whole application.