As others have mentioned the @param you are referring to is part of a comment and not syntactically significant. It is simply there to provide hints to a documentation generator. You can find more information on the supported directives and syntax by looking at the PHPDoc project.
Speaking to the second part of your question... As far as I know, there is not a way to specify the return type in PHP. You also can't force the parameters to be of a specific primitive type (string, integer, etc).
You can, however, required that the parameters be either an array, an object, or a specific type of object as of PHP 5.1 or so.
function importArray(array $myArray)
{
}
PHP will throw an error if you try and call this method with anything besides an array.
class MyClass
{
}
function doStuff(MyClass $o)
{
}
If you attempt to call doStuff with an object of any type except MyClass
, PHP will again throw an error.