Add taxonomie to WP

taxonomie.php

<?php

// Doc: https://codex.wordpress.org/Function_Reference/register_taxonomy 

register_taxonomy('portfolio_tag','portfolio',array(
'hierarchical' => false,
'labels' => array(
    'name' => _x( 'Tags', 'taxonomy general name' ),
    'singular_name' => _x( 'Tag', 'taxonomy singular name' ),
    'search_items' =>  __( 'Search Tags' ),
    'popular_items' => __( 'Popular Tags'),
    'all_items' => __( 'All Tags'),
    'parent_item' => null,
    'parent_item_colon' => null,
    'edit_item' => __( 'Edit Tag'), 
    'update_item' => __( 'Update Tag'),
    'add_new_item' => __( 'Add New Tag'),
    'new_item_name' => __( 'New Tag Name'),
    'separate_items_with_commas' => __( 'Separate Tag with commas'),
    'add_or_remove_items' => __( 'Add or remove Tag'),
    'choose_from_most_used' => __( 'Choose from the most used Tag')
),
'show_ui' => true,
'show_in_menu' => true, 
'query_var' => true,
'rewrite' => false,
'show_tagcloud' => true
));