PRG-2

$use_prg = new prg_pattern();

class prg_pattern {
    public function __construct() {
        add_action( 'template_redirect', array( $this, 'prg_get_and_redirect' ) );
        add_shortcode( 'prgpattern', array( $this, 'prg_pattern_form' ) );
    }


    public function prg_pattern_form( $atts ){
        $atts = shortcode_atts(
            array(
                'slug' => 'noFoo',
                'title' => 'noBob',
                'extern' => 'false'
            ), $atts, 'prgpattern' );

        if ( $atts['extern'] == 'true' ) {
            $redirect_slug = esc_url( $atts['slug'] );
        } else {
            $redirect_slug = esc_url( home_url() . '/' . strtolower( $atts['slug'] ) );
        }

        ob_start();
        ?>
            <form method="POST">
                <button class="noLink" type="submit" name="prgpattern" value="<?php echo $redirect_slug; ?>"><?php echo $atts['title']; ?></button>
            </form>
        <?php
        return ob_get_clean();
    }


    public function prg_get_and_redirect(){
        if ( isset( $_POST['prgpattern'] ) ) {
            $slug = esc_url( $_POST['prgpattern'] );
            wp_redirect( $slug );
            exit();
        }
    }
}