function tapro_register_cpts() {
    register_post_type('continent', array(
        'labels' => array('name' => __('Continents', 'tourism-advanced-pro')),
        'public'      => true,
        'hierarchical'=> true,
        'has_archive' => true,
        'rewrite'     => array('slug' => ''),
        'supports'    => array('title', 'editor', 'thumbnail', 'custom-fields')
    ));

    register_post_type('country', array(
        'labels' => array('name' => __('Countries', 'tourism-advanced-pro')),
        'public'      => true,
        'hierarchical'=> true,
        'has_archive' => true,
        'rewrite'     => array('slug' => ''),
        'supports'    => array('title', 'editor', 'thumbnail', 'custom-fields')
    ));

    register_post_type('destination', array(
        'labels' => array('name' => __('Destinations', 'tourism-advanced-pro')),
        'public'      => true,
        'hierarchical'=> true,
        'has_archive' => true,
        'rewrite'     => array('slug' => ''),
        'supports'    => array('title', 'editor', 'thumbnail', 'custom-fields')
    ));
}
add_action('init', 'tapro_register_cpts');
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<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /home/arab/public_html/wp-content/plugins/tourism-suite/includes/cpt.php:1) in <b>/home/arab/public_html/wp-includes/pluggable.php</b> on line <b>1435</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /home/arab/public_html/wp-content/plugins/tourism-suite/includes/cpt.php:1) in <b>/home/arab/public_html/wp-includes/pluggable.php</b> on line <b>1438</b><br />