On the Planet SoC blog today, there's this look at how ifehhali added foreign key support to the MDB2_Schema_Writer as a part of his Summer of Code project to improve the PEAR::MDB2_Schema package.

MDB2_Schema_Writer is the responsible for dumping a database schema to a XML file. It walks into a database definition and outputs the correspondent XML tags.

He gives an example of checking a table (in $table) to see if it has constraints and check its validity. If everything's okay, the script pushes data into a buffer of specially formatted XML data.