how to add multi select category in visual composer - wordpress

Question

How can I add a multi-selector for the Visual composer?
vc_map( array(
"name" => esc_html__("Ajax Posts", '7mag'),
"base" => "YT_ajaxpost",
"icon" => "YT_vc_ico_ajaxpost",
"class" => "YT_vc_sc_ajaxpost",
"category" => esc_html__("7mag", '7mag'),
"params" => array(
array(
"type" => "dropdown",
"heading" => esc_html__("Style", '7mag'),
"param_name" => "multiple",
"value" => $categories_array,
),
) );
For example:
link

Answer 1

You need to register new shortcode attribute.
// Create multi dropdown param type
vc_add_shortcode_param( 'dropdown_multi', 'dropdown_multi_settings_field' );
function dropdown_multi_settings_field( $param, $value ) {
$param_line = '';
$param_line .= '<select multiple name="'. esc_attr( $param['param_name'] ).'" class="wpb_vc_param_value wpb-input wpb-select '. esc_attr( $param['param_name'] ).' '. esc_attr($param['type']).'">';
foreach ( $param['value'] as $text_val => $val ) {
if ( is_numeric($text_val) && (is_string($val) || is_numeric($val)) ) {
$text_val = $val;
}
$text_val = __($text_val, "js_composer");
$selected = '';
if(!is_array($value)) {
$param_value_arr = explode(',',$value);
} else {
$param_value_arr = $value;
}
if ($value!=='' && in_array($val, $param_value_arr)) {
$selected = ' selected="selected"';
}
$param_line .= '<option class="'.$val.'" value="'.$val.'"'.$selected.'>'.$text_val.'</option>';
}
$param_line .= '</select>';
return $param_line;
}
Then use it:
array(
"type" => "dropdown_multi",
"heading" => esc_html__("Style", '7mag'),
"param_name" => "multiple",
"value" => $categories_array,
),

Answer 2

I've updated the above solution. due to $value!=='' check the values were not being selected after save.
function dropdown_multi_settings_field( $param, $value ) {
if ( ! is_array( $value ) ) {
$param_value_arr = explode( ',', $value );
} else {
$param_value_arr = $value;
}
$param_line = '';
$param_line .= '<select multiple name="' . esc_attr( $param['param_name'] ) . '" class="wpb_vc_param_value wpb-input wpb-select ' . esc_attr( $param['param_name'] ) . ' ' . esc_attr( $param['type'] ) . '">';
foreach ( $param['value'] as $text_val => $val ) {
if ( is_numeric( $text_val ) && ( is_string( $val ) || is_numeric( $val ) ) ) {
$text_val = $val;
}
$selected = '';
if ( ! empty( $param_value_arr ) && in_array( $val, $param_value_arr ) ) {
$selected = ' selected="selected"';
}
$param_line .= '<option class="' . $val . '" value="' . $val . '"' . $selected . '>' . $text_val . '</option>';
}
$param_line .= '</select>';
return $param_line;
}
vc_add_shortcode_param( 'dropdown_multi', 'dropdown_multi_settings_field' );