What is a dereferencable scalar in PHP?

Question

Recently, I was following this PHP talk ^{See it on YouTube}. There is a part about new features in PHP7 that is a really strange stuff for me (in "Uniform variable syntax" part of the talk), which wrote:

// support all operations on dereferencable scalars
// (not very useful)
"string"->toLower()

What is a dereferencable scalar? I know when I call a method on a non-object, for example:

echo "string"->toLower();

I'll get the following Error in PHP7:

Fatal Error: Uncaught Error: Call to a member function toLower() on string

Also, I cannot find a way to declare methods on strings (like something we see in JavaScript); as I know, there is no way to do it.

So, what is the code above saying? How can we do the stuff above? What is the use case for it? Saying it generally, what is "string"->toLower()?

(Editted) Note: While the PHP talks says it exists as of PHP 7.0, it seems to be a mistake by Mr. Lerdorf (it could be a rejected patch, for example).

Thanks in advance.

Answer 1

Short answer: this would be a syntax sugar.

Longer answer: This is a way to call functions with the syntax which aligns with the object syntax.

For example, an object (i.e. a class instance) could have a method called "length()". The invocation of this method would be expressed with the following "arrow" syntax:

$length = $myObject->length();

But, for example, to get a length of a string, you can't currently use the same syntax, because strings are not objects. Instead, you must put the variable name within the parentheses, as a parameter to the strlen function , i.e.:

$length = strlen($myString);

What you have mentioned is an idea to unify the syntax, i.e.

$length = $myString->strlen();

would be another possible syntax to call the strlen function. This would make operations on scalars (and arrays) syntactically closer to the objects' method calls.

Note that PHP doesn't support this syntax yet, as of 2018-09-14.