<?php
/**
 * PSR-4 compliant class autoloader
 *
 * @see https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-4-autoloader.md
 * @link https://www.php.net/manual/en/function.spl-autoload-register.php
 * @param string $class fully-qualified class name
 * @return void
 */
spl_autoload_register(function ($class) {

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

    // base directory for the namespace prefix
    $base_dir = 'src/';

    // normalize the base directory with a trailing separator
    $base_dir = rtrim($base_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
    $relative_class = substr($class, $len);

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

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