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
{
    //
}

There can be problems when a multiple of 512 lands in the middle of the class name. you can resolve it by making sure the class name was not the last token parsed by the token_get_all. Simplest way I found was to decrement a counter on every token, and set the counter to 2 when you find the class name. Then do if ($namespace && $class && $lastTokenIsClassNameCounter !== 1) {. That way if your class name was the last token in the buffer, and it may have gotten split, you do at least one more read from the file. Won't work if your php file is malformed, but then your php file is malformed :)