PHP For循环中的if语句不起作用

Question

I'm trying to add the CSS class "selected" to the first accordionButton div created. Why doesn't this work?

// Create nav from database
                $chapter_array = get_chapter_names();

                for ($i=0; $i < sizeof($chapter_array); $i++) { 
                    if($i == 0) {
                        $selected = 'selected';
                    }
                    echo '<div class="accordionButton '.$selected.'">'.$chapter_array[$i].'</div>';

                    $page_id_array = get_page_ids($i);

                    echo '<div class="accordionContent">';
                    for ($j=0; $j < sizeof($page_id_array); $j++) { 
                        $page_name = get_page_name($page_id_array[$j]);
                        echo '<a href="?page_id='.$page_id_array[$j].'">'.$page_name.'</a><br />';
                    }
                    echo '</div>';
                }

Answer 1

You never set $selected back after the first div so this adds that class to every div, because $selected always contains the string 'selected' .

You can set it to the empty string before your if statement:

$selected = '';
if($i == 0) {
    $selected = 'selected';
}

If you like this better you can also write that as a nice ternary expression:

$selected = $i == 0 ? 'selected' : '';

Answer 2

Declare $selected outside of the loop too:

            $chapter_array = get_chapter_names();
            $selected = '';

            for ($i=0; $i < sizeof($chapter_array); $i++) { 
                if($i == 0) {
                    $selected = 'selected';
                }
                echo '<div class="accordionButton '.$selected.'">'.$chapter_array[$i].'</div>';

                $page_id_array = get_page_ids($i);

                echo '<div class="accordionContent">';
                for ($j=0; $j < sizeof($page_id_array); $j++) { 
                    $page_name = get_page_name($page_id_array[$j]);
                    echo '<a href="?page_id='.$page_id_array[$j].'">'.$page_name.'</a><br />';
                }
                echo '</div>';
            }

Also, this is a lil bit prettier (:

$selected = $i == 0 ? 'selected' : '';