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Error Identifier: preDec.nonNumeric

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(string $s): void
{
	--$s;
}

Why is it reported? #

The pre-decrement operator -- is intended for numeric types. Applying it to a non-numeric value such as string, bool, null, or an object does not produce meaningful results and is likely a bug.

This error is reported by phpstan/phpstan-strict-rules.

How to fix it #

Convert the value to an appropriate numeric type before decrementing, or use explicit arithmetic:

 <?php declare(strict_types = 1);
 
-function doFoo(string $s): void
+function doFoo(int $count): void
 {
-	--$s;
+	--$count;
 }

How to ignore this error #

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

// @phpstan-ignore preDec.nonNumeric
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.nonNumeric

Rules that report this error #

• PHPStan\Rules\Operators\OperandInArithmeticIncrementOrDecrementRule [1] phpstan/phpstan-strict-rules

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