Get the FQCN from a PHP file specified by file path

fqcn_from_path.php

<?php

public static function fqcnFromPath(string $path): string
{
    $namespace = $class = $buffer = '';

    $handle = fopen($path, 'r');

    while (!feof($handle)) {
        $buffer .= fread($handle, 512);

        // Suppress warnings for cases where `$buffer` ends in the middle of a PHP comment.
        $tokens = @token_get_all($buffer);

        // Filter out whitespace and comments from the tokens, as they are irrelevant.
        $tokens = array_filter($tokens, fn($token) => $token[0] !== T_WHITESPACE && $token[0] !== T_COMMENT);

        // Reset array indexes after filtering.
        $tokens = array_values($tokens);

        foreach ($tokens as $index => $token) {
            // The namespace is a `T_NAME_QUALIFIED` that is immediately preceded by a `T_NAMESPACE`.
            if ($token[0] === T_NAMESPACE && isset($tokens[$index + 1]) && $tokens[$index + 1][0] === T_NAME_QUALIFIED) {
                $namespace = $tokens[$index + 1][1];
                continue;
            }

            // The class name is a `T_STRING` which makes it unreliable to match against, so check if we have a
            // `T_CLASS` token with a `T_STRING` token ahead of it.
            if ($token[0] === T_CLASS && isset($tokens[$index + 1]) && $tokens[$index + 1][0] === T_STRING) {
                $class = $tokens[$index + 1][1];
            }
        }

        if ($namespace && $class) {
            // We've found both the namespace and the class, we can now stop reading and parsing the file.
            break;
        }
    }

    fclose($handle);

    return $namespace.'\\'.$class;
}

Based on my testing this works for the following examples:

namespace Foo\Bar;

use Bin\Qux;

class YourClass extends SomeOtherClass
{
    //
}

namespace Foo\Bar {
    use Bin\Qux;

    class YourClass extends SomeOtherClass
    {
        //
    }
};

and even some wonky whitespace or comments:

namespace Foo\Bar;

use Bin\Qux;

class

// I am a comment

YourClass
{
    //
}