How to use an array of categories as a dropdown?

Question

I need to use an array of existing categories as a dropdown option value then use the selected category ID. More exactly, I try to make a custom module to display the latest posts form selected category using Visual Composer plugin tutorial.

I tried to use wp_dropdown_categories in the follwoing code but I get some errors and nothing works:

        array(
        'param_name'    => 'category_id',
        'type'          => 'dropdown',
        'value'         => wp_dropdown_categories, // here I'm stuck
        'heading'       => __('Category filter:', 'overmax'),
        'description'   => '',
        'holder'        => 'div',
        'class'         => ''
        ),

Thanks

Answer 1

Try this,

$categories_array = array();
$categories = get_categories();
foreach( $categories as $category ){
  $categories_array[] = $category->term_id;
}

array(
  'param_name'    => 'category_id',
  'type'          => 'dropdown',
  'value'         => $categories_array, // here I'm stuck
  'heading'       => __('Category filter:', 'overmax'),
  'description'   => '',
  'holder'        => 'div',
  'class'         => ''
),

Answer 2

In addtion to the answer, if you want that you dropdown value has the id of the category you should do something like this:

$categories_array = array();
$categories = get_terms('tax_id', array('hide_empty' => false));
foreach( $categories as $category ){
  $categories_array[$category->name] = $category->term_id; 
}