Could not check compatibility between extensions

[supercomputer276]

I'm attempting to make an inline extension in PHP that apply span tags to text inside a pair of curly braces, but first I want to make sure I have everything set up right to do a passthrough - as in, it runs without changing anything. At this, I am running into an error I can't figure out. (All names for my functions and files changed for privacy.)

The error:

Fatal error: Could not check compatibility between MyExtension::register(League\CommonMark\Environment\ConfigurableEnvironmentInterface $environment): void and League\CommonMark\Extension\ExtensionInterface::register(League\CommonMark\Environment\EnvironmentBuilderInterface $environment): void, because class League\CommonMark\Environment\ConfigurableEnvironmentInterface is not available in /var/www/html/myscript.php on line 25

The script:

<?php
	require __DIR__ . '/vendor/autoload.php';
	use League\CommonMark\Extension\ExtensionInterface;
	use League\CommonMark\Environment\ConfigurableEnvironmentInterface;
	use League\CommonMark\Environment\Environment;
	use League\CommonMark\Extension\CommonMark\CommonMarkCoreExtension;
	use League\CommonMark\MarkdownConverter;
	use League\CommonMark\Parser\Inline\InlineParserInterface;
	use League\CommonMark\Parser\Inline\InlineParserMatch;
	use League\CommonMark\Parser\InlineParserContext;
	
	class MyParser implements InlineParserInterface {
		public function getMatchDefinition(): InlineParserMatch {
			//all capital letters, plus whitespace, commas, question marks, and exclamation points, inside a pair of curly braces
			return InlineParserMatch::regex('\{\{([A-Z|\s|,|\?|\!]*)\}\}');
		}
		
		public function parse(InlineParserContext $inlineContext): bool {
			return false; //planning to handle this once a passthrough works
		}
	}
	
	final class MyExtension implements ExtensionInterface
	{
		public function register(ConfigurableEnvironmentInterface $environment): void  //<-- the line referenced by the error
		{
			$environment->addInlineParser(new MyParser());
		}
	}
	
	$environment = new Environment();
	$environment->addExtension(new CommonMarkCoreExtension());
	$environment->addExtension(new MyExtension());

	$converter = new MarkdownConverter($environment);
?>

I'm not sure why it's giving the error it does, because Environment\ConfigurableEnvironmentInterface is being included.

My PHP version is 7.4.3.

[colinodell]

I don't know why PHP can't find that class, but using EnvironmentBuilderInterface $environment as the parameter on that line should fix this.

[supercomputer276]

Yeah, that turned out to be it. The documentation on Customizations/Extensions is either wrong or for I thought I got the latest version but I don't for some reason. Honestly, most of the documentation when it comes to custom extensions leaves a lot to be desired.