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The best way to understand what a hook does is to look at where it occurs in the source code.
do_action( "hook_name" )apply_filters( "hook_name", "what_to_filter" ).Remember, this hook may occur in more than one file. Moreover, the hook's context may change from version to version.
This hook occurs 3 times in this file.
| Line | Code |
|---|---|
| 396 | * 'show_option_none', 'show_option_all', and various forms of the |
| 397 | * term name. |
| 398 | * |
| 399 | * @since 1.2.0 |
| 400 | * |
| 401 | * @see wp_dropdown_categories() |
| 402 | * |
| 403 | * @param string $element Taxonomy element to list. |
| 404 | */ |
| 405 | $show_option_none = apply_filters( 'list_cats', $r['show_option_none'] ); |
| 406 | $output .= "\t<option value='" . esc_attr( $option_none_value ) . "' selected='selected'>$show_option_none</option>\n"; |
| 407 | } |
| 408 | |
| 409 | if ( ! empty( $categories ) ) { |
| 410 | |
| 411 | if ( $r['show_option_all'] ) { |
| 412 | |
| 413 | /** This filter is documented in wp-includes/category-template.php */ |
| 414 | $show_option_all = apply_filters( 'list_cats', $r['show_option_all'] ); |
| 415 | $selected = ( '0' === strval($r['selected']) ) ? " selected='selected'" : ''; |
| 416 | $output .= "\t<option value='0'$selected>$show_option_all</option>\n"; |
| 417 | } |
| 418 | |
| 419 | if ( $r['show_option_none'] ) { |
| 420 | |
| 421 | /** This filter is documented in wp-includes/category-template.php */ |
| 422 | $show_option_none = apply_filters( 'list_cats', $r['show_option_none'] ); |
| 423 | $selected = selected( $option_none_value, $r['selected'], false ); |
| 424 | $output .= "\t<option value='" . esc_attr( $option_none_value ) . "'$selected>$show_option_none</option>\n"; |
| 425 | } |
| 426 | |
| 427 | if ( $r['hierarchical'] ) { |
| 428 | $depth = $r['depth']; // Walk the full depth. |
| 429 | } else { |
| 430 | $depth = -1; // Flat. |
| 431 | } |