Wordpress Autoload classes

wp-theme.php

/**
 * WordPress Autoload classes.
 */
spl_autoload_register( function ( $full_class_name ) { //phpcs:ignore PEAR.Functions.FunctionCallSignature
    if ( strpos( $full_class_name, __NAMESPACE__  ) !== 0 ) { // . '\Core'
        return; // Not in the plugin namespace, don't check.
    }
    $full_class_name = strtolower( str_replace( '_', '-', $full_class_name ) );
    $class_parts     = explode( '\\', $full_class_name );
    unset( $class_parts[0] ); // Unset the __NAMESPACE__.

    $class_file    = 'class-' . array_pop( $class_parts ) . '.php';
    $class_parts[] = $class_file;

    require_once plugin_dir_path( __FILE__ ) . implode( DIRECTORY_SEPARATOR, $class_parts );
} );//phpcs:ignore PEAR.Functions.FunctionCallSignature