unaryOp.invalid

Code example

<?php declare(strict_types = 1);

function doFoo(array $a): void
{
	-$a;
}

Why is it reported?

A unary operator (+, -, or ~) is applied to a value whose type does not support that operation. PHP's unary operators have specific type requirements:

• + (unary plus) and - (unary minus) require a numeric type (int, float, or a string that can be converted to a number).
• ~ (bitwise not) requires an int, float, or string.

Applying these operators to incompatible types like arrays, objects, or resources results in a runtime error.

How to fix it

Ensure the operand has a type compatible with the unary operator.

-function doFoo(array $a): void
+function doFoo(int $a): void
 {
 	-$a;
 }

Or convert the value to an appropriate type before applying the operator:

 function doFoo(string $value): void
 {
-	-$value;
+	-(int) $value;
 }