autoloader for custom stream wrappers

Description

Would it be possible to add an autoloader/callback function if a call is made to a function using a stream wrapper protocol that is not yet defined?

Currently, if you access a stream protocol not registered, a warning is logged 'Unable to find the wrapper "abc" - did you forget to enable it when you configured PHP?'.

In the below example, since abc hasn't yet been registered with stream_wrapper_register(), the new function stream_wrapper_autoload() would be called where abc would be registered and allow the file_get_contents() call to complete.

<?php
stream_wrapper_autoload(function($protocol)
{
	switch ($protocol)
	{
		case 'abc':
			stream_wrapper_register('abc', 'abc');
			break;
	}
});

$a = file_get_contents('abc://file.txt');
?>

I am using the AWS S3 stream wrapper (https://docs.aws.amazon.com/sdk-for-php/v3/developer-guide/s3-stream-wrapper.html). Using this custom stream wrapper currently requires me either to:

• register the stream wrapper on every request even if it won't be used on the given request
• or register it before any call that would use it (file_get_contents, fopen, copy, etc).
• or add a wrapper function around file_get_contents and the other file functions to check first if the stream wrapper is registered by calling stream_get_wrappers().

Having an autoload function would allow me to register the stream wrapper only when it's needed.

Thank you for your help.

Ryan

Start by tracing unresolved stream protocols through file_get_contents(), fopen(), and copy(), and review how stream_wrapper_register() and stream_get_wrappers() currently handle registration. Define the callback behavior and its interaction with failed lookups, then verify that a wrapper registered by the callback allows the original file operation to complete.