plus.leftNonNumeric

Code example

<?php declare(strict_types = 1);

function doFoo(): void
{
	$null = null;
	$result = $null + 5;
}

Why is it reported?

The + operator in PHP is intended for numeric arithmetic (or array union). When a non-numeric value such as null, an object, or a non-numeric string is used on the left side of the + operator, PHP will attempt implicit type coercion, which is error-prone and usually indicates a bug.

In the example above, null is used on the left side of the + operator, which PHP silently coerces to 0.

This rule is provided by the phpstan-strict-rules package.

How to fix it

Ensure the left operand is a numeric type (int, float, or numeric string):

 <?php declare(strict_types = 1);

-function doFoo(): void
+function doFoo(int $value): void
 {
-	$null = null;
-	$result = $null + 5;
+	$result = $value + 5;
 }

Or explicitly convert the value to a number first:

 <?php declare(strict_types = 1);

 function doFoo(?int $value): void
 {
-	$result = $value + 5;
+	$result = ($value ?? 0) + 5;
 }