PHP RFC: Warn on conversions from resource to string

• Version: 0.1
• Date: 2024-09-24
• Author: Gina Peter Banyard girgias@php.net
• Status: Under Discussion
• Target Version: PHP 8.5
• Implementation: https://github.com/php/php-src/pull/16022
• First Published at: https://wiki.php.net/rfc/warn-resource-to-string

PHP has a history of performing various forms of type conversions. While most dubious cases of such conversions nowadays throw a TypeError, or at least emit an E_WARNING, the conversion of resources to strings does none of these things.

As a consequence it is possible to concatenate a resource with a string without any errors, but performing any sort of arithmetics with it throws a TypeError:

<?php
 
var_dump(STDERR . 'hello');
var_dump(STDERR + 10);
 
?>

will result in:

string(19) "Resource id #3hello"

Fatal error: Uncaught TypeError: Unsupported operand types: resource + int in FILE

This is surprising behaviour, especially as a non-stringable object being used with the concatenation operator would throw an Error.

Considering that resources are being phased out in favour of opaque objects and do not support being converted to strings. We propose to align the behaviour with that of converting an array to string, which is to emit a warning on implicit and explicit conversions.

Emit an E_WARNING when a conversion from resource to string occurs. Some common situations where this can occur:

• String concatenation
• String interpolation
• echo
• (string) cast

As warnings could be promoted to an exception via an error handler, this may result in exceptions being thrown in place where none previously could.

Next minor version, PHP 8.5.

As per the voting RFC a yes/no vote with a 2/3 majority is needed for this proposal to be accepted.

Voting started on 2024-XX-XX and will end on 2024-XX-XX.

• Promote warning to a TypeError