Add documentation for WordPress.PHP.RestrictedPHPFunctions

[gogdzl]

Related to #1722

[GaryJones]

Suggested change

	add_action( 'init', function() {
	return foo( 'bar' );
	} );
	add_action( 'init', <em>function() {
	return foo( 'bar' );
	}</em> );

We can highlight the good bit of this snippet to focus on.

[rodrigoprimo]

Thanks for another PR adding user documentation for a sniff, @gogdzl! I left some comments with suggestions for us to discuss.

[rodrigoprimo]

Suggested change

	The restricted function create_function() should not be used.
	The function create_function() should not be used.

[rodrigoprimo]

I wonder if it is a good idea to include an example with a declared named function as well (and then also update the title attribute)? Maybe it is just me, but it took me a second to properly read the sentence Please use declared named or anonymous functions instead. and to realize that functions applies to both declared named and anonymous. My first thought was "what is a declared named"?

[rodrigoprimo]

I'm not against mentioning here that anonymous functions are also known as closure. But if it is important to provide this information, I believe it should also be present in the description of the <standard> block.

[rodrigoprimo]

I'm unsure if including a call to add_action() here helps understand what the sniff does or if it just adds noise. Usually, the examples are minimalistic, and just calling calling create_function() or calling it and assigning the returned value to a variable is enough?