Autoloader PSR-4 is correspond PSR-2 class name

autoloader-psr4-for-psr-2-class-name.php

spl_autoload_register(function ($class) {

    // project-specific namespace prefix
    $prefix = 'RMLcustomizer\\';

    // base directory for the namespace prefix
    $baseDir = __DIR__ . DIRECTORY_SEPARATOR;

    // does the class use the namespace prefix?
    $len = strlen($prefix);
    if (strncmp($prefix, $class, $len) !== 0) {
        // no, move to the next registered autoloader
        return;
    }

    // get the relative class name
    $relativeClass = substr($class, $len);
    
    // build specific path
    // First letter is no matter 
    $relativeFile = $relativeClass[0];

    for ($position = 1; $position < strlen($relativeClass); $position++) {
        // Latter has upper case
        if (ctype_upper($relativeClass[$position])) {
            // and is not namespace divider
            if (false === in_array($relativeClass[$position - 1], array('\\', '/'))) {
                $relativeFile .= '-' . $relativeClass[$position];
                continue;
            }
        }

        $relativeFile .= $relativeClass[$position];
    }

    // replace the namespace prefix with the base directory, replace namespace
    // separators with directory separators in the relative class name, append
    // with .php
    $file = strtolower($baseDir . str_replace('\\', '/', $relativeFile) . '.php');

    // if the file exists, require it
    if (file_exists($file)) {
        require $file;
    }
});

For example, I have file path ./hook/post-details.php. It file consist class postDetails. Default psr-4 example isn't work. My code is work for this case.