The file php_barebones_alt.php contains a bare-bones PHP tutorial for anyone wanting to get up and running with PHP while structuring their code for proper documentation with doxygen, a code documentation generator. (If your are reading the source code of the file directly, the comments in it are formatted for used by doxygen.)

This file is a minor adaption of php_barebones.php, the actual PHP tutorial on this site. The only significant changes are that some lines of PHP are rewritten (encasing them in functions) so that doxygen will document the code correctly. For more info see page Global-scope statements and doxygen.

When this page is served up via a web server that runs PHP, you get the tutorial and can even interact with some of its examples. PHP is used to handle the interactions.