Merge pull request #1 from sguazt/master

Bad URL parameter for 'OlderStories.php'
[php] (change) Added methods 'getSessionPostGetParam'/'getSessionGetPostParam' as helpers for getting session parameters
[php] (bug-fix) Wrong variable name introduced in the last commit: 'category' => 'categoryId'
[php] (bug-fix) Wrong session parameter name introduced in the last commit: 'categoryId' => 'category'
[php] (bug-fix) HTML document type definition was not conformant to W3C standard
[php] (change) Cosmetic changes: style for error messages confined in the 'printError' function
Merge branch 'master' of https://github.com/sguazt/RUBBoS into php-dev