Multi-programming-language "cookbook", sample CGI code

Check whether a given parameter has been supplied, if so then (1) get the value of that parameter as a string, (2) display that value as text, and (3) check whether it's the correct string:
PHP
Validate decimal integer in field within submitted HTML form:
PHP / perl / lisp / c / c++ / java
(Correct format is: Optional whitespace, optional sign, one or more consecutive digits, optional whitespace. Try various of those options in the form. Also try putting garbage characters or extra whitespace in various places.)
Note: Except for fetching the HTML form contents itself, this code would work equally well to validate user input via standard input. But by necessity, all these demos run via the Web and take input via HTML forms (or equivalently by manually-entered query strings that look like encoded form contents).
Set cookie, then later look for that cookie and fetch its value: PHP
(Anybody who knows how to do all this per current practice in any of the other languages, please submit code snippets that I can test myself and then include in sample demo here.)
To do: Generate Latin-1 output
To do: Generate UTF-8 output for alphabet-based languages
To do: Generate UTF-8 output for Chinese characters