Error Identifier: preDec.expr

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

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;

How to ignore this error #

You can use the identifier preDec.expr to ignore this error using a comment:

// @phpstan-ignore preDec.expr
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: preDec.expr

Rules that report this error #

PHPStan\Rules\Operators\InvalidIncDecOperationRule [1]

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