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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 |
|---|---|
| 435 | * 'show_option_none', 'show_option_all', and various forms of the |
| 436 | * term name. |
| 437 | * |
| 438 | * @since 1.2.0 |
| 439 | * |
| 440 | * @see wp_dropdown_categories() |
| 441 | * |
| 442 | * @param string $element Taxonomy element to list. |
| 443 | */ |
| 444 | $show_option_none = apply_filters( 'list_cats', $r['show_option_none'] ); |
| 445 | $output .= "\t<option value='" . esc_attr( $option_none_value ) . "' selected='selected'>$show_option_none</option>\n"; |
| 446 | } |
| 447 | |
| 448 | if ( ! empty( $categories ) ) { |
| 449 | |
| 450 | if ( $r['show_option_all'] ) { |
| 451 | |
| 452 | /** This filter is documented in wp-includes/category-template.php */ |
| 453 | $show_option_all = apply_filters( 'list_cats', $r['show_option_all'] ); |
| 454 | $selected = ( '0' === strval($r['selected']) ) ? " selected='selected'" : ''; |
| 455 | $output .= "\t<option value='0'$selected>$show_option_all</option>\n"; |
| 456 | } |
| 457 | |
| 458 | if ( $r['show_option_none'] ) { |
| 459 | |
| 460 | /** This filter is documented in wp-includes/category-template.php */ |
| 461 | $show_option_none = apply_filters( 'list_cats', $r['show_option_none'] ); |
| 462 | $selected = selected( $option_none_value, $r['selected'], false ); |
| 463 | $output .= "\t<option value='" . esc_attr( $option_none_value ) . "'$selected>$show_option_none</option>\n"; |
| 464 | } |
| 465 | |
| 466 | if ( $r['hierarchical'] ) { |
| 467 | $depth = $r['depth']; // Walk the full depth. |
| 468 | } else { |
| 469 | $depth = -1; // Flat. |
| 470 | } |