PHP RFC: Apprise on Invalid Arithmetic Operands

• Version: 0.1
• Date: 2016-04-06
• Author: Thomas Punt, tpunt@php.net
• Status: Draft
• First Published at: https://wiki.php.net/rfc/apprise_on_invalid_arithmetic_operands

Following on from the warning about invalid strings in arithmetic RFC, this RFC proposes to warn developers when they are using invalid operands with the arithmetic operators. The overall aim is therefore to help developers catch mistakes in their code when doing something non-sensical.

This is a WIP. Feel free to update this RFC with other cases where you'd like to see E_WARNINGs or E_NOTICEs emitted (as well as cases of promoting E_NOTICEs or demoting E_WARNINGs).

EDIT related: https://bugs.php.net/bug.php?id=67904

This RFC seeks to do the following:

var_dump(1 + fopen(__FILE__, 'r')); // currently outputs int(6)

Reasoning: It is non-sensical behaviour to want to use a resource's ID, particularly without even notifying the programmer (†).

var_dump(1 + null); // currently outputs int(1)

Reasoning: If empty strings (“”) now emit an E_WARNING, then other non-numeric falsy values should too

var_dump(1 + new StdClass); // currently outputs int(2) && Notice: Object of class stdClass could not be converted to int...

Reasoning: The coercion is completely non-sensical. It will always coerce an object to int(1) in this context (†), and so the error level should be raised.

(†) Even this, I feel is non-sensical. If other truthy values (such as “abc”) are coerced to int(0), then both objects and resources should too. Right now, objects coerce to int(1), and resource coerces to their resource ID. For now though, this is considered out of the scope of this RFC.

What breaks, and what is the justification for it?

PHP 7.1

Describe the impact to CLI, Development web server, embedded PHP etc.

Will existing extensions be affected?

To be done...

None.

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