preDec.expr

Code example

<?php declare(strict_types = 1);

function doFoo(): int
{
	return 5;
}

--doFoo();

Why is it reported?

The decrement operator (--) is applied to an expression that is not a variable. The -- operator requires an assignable expression (a variable, array element, or property). In the example above, doFoo() is a function call result, which cannot be decremented.

How to fix it

Apply the operator to a variable instead:

 <?php declare(strict_types = 1);

---doFoo();
+$value = doFoo();
+--$value;