All PHP Dereferencements¶
This ugly expression holds a long list of operators to move from one value to the other and produces the simple letter ‘c’. Can you recognize them all?
First :: is a static constant, with its class on the left, and constant on the right.
The first -> works on a class constant, once the constant is an object. This takes a slight detour by a global constant, and it works. It allows to call a property. This property is reached with a dynamic property name: this introduces the curly braces notation. That dynamic property name is actually a single string, but it is also stored into a local variable: because, why not?
The next operator is the array syntax [1], which accesses the element numbered 1 in the previous array.
Then, this element turns out to be a callback. The callback may be called directly, with the parenthesis (), but it may also be called indirectly with the callable notation (...): this produces a closure, based on the previous callable. In this expression, it actually has no effect.
The result of the callable may, or may not, be an object. This is handled by ?->. If it is not, then the whole expression is actually null. If it is an object, then the evaluation continues with yet another property.
There, there is a second dynamic property, build on top of the first $p and another variable, which is also assigned while being concatenated. This is the p2 property.
Since the p2 property exists on the object of class D, the expression uses the static :: operator again. This time, it is not a constant, but a case from an enumeration. There is no way to distinguish cases and constant at call time.
The enumeration F is backed by a string, so this automatically introduces properties to the enumeration objects, name and value. Here, the second -> operator reaches to this implicitly declared property.
Finally, value produces a string, and strings accept the array syntax. [$c] is actually [2], as $c was assigned the value 2, and this was done at bit earlier in the expression.
At the end, there is one of the most convoluted literal c character.
See Also¶
Can you understand this? [Try me]