minus.rightNonNumeric

Code example

<?php declare(strict_types = 1);

function doFoo(int $a, bool $flag): void
{
	$result = $a - $flag;
}

Why is it reported?

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

The right-hand side operand of a subtraction (-) is not a numeric type. PHP's subtraction operator expects both operands to be numeric (int or float). Using a non-numeric type such as bool, null, array, or object on the right side of a subtraction will produce unexpected results or a TypeError in strict mode.

How to fix it

Ensure the right-hand operand is a numeric type by narrowing the type:

 <?php declare(strict_types = 1);

-function doFoo(int $a, bool $flag): void
+function doFoo(int $a, int $b): void
 {
-	$result = $a - $flag;
+	$result = $a - $b;
 }

Or cast the value before use:

 <?php declare(strict_types = 1);

 function doFoo(int $a, bool $flag): void
 {
-	$result = $a - $flag;
+	$result = $a - (int) $flag;
 }