select box에서 값을 선택했을때 

다른 select box의 선택 옵션들이 변경되게 하려고 하는데 방법이 있을까요?

현재는 이렇게 짰는데 제가봐도 틀린거 같네요

<?php if ($is_category) { ?>
<div class="bo_w_select write_div">
    <label for="ca_name" class="sound_only">분류<strong>필수</strong></label>
    <select name="ca_name" id="ca_name" required>
        <option value="">분류를 선택하세요</option>
        <?php echo $category_option ?>
    </select>
</div>
    <div class="bo_w_tit write_div">
        <label for="wr_2" class="sound_only">중분휴<strong>필수</strong></label>
        <select name="ca_name" id="ca_name" required>
            <?php if ($ca_name='인간/생활') { ?>
                <option value="명칭">명칭</option>
                <option value="감정/성격">감정/성격</option>
                <option value="미용/패션">미용/패션</option>
                <option value="음식/요리">음식/요리</option>
                <option value="주거/생활">주거/생활</option>
                <option value="문화/예술">문화/예술</option>
                <option value="건강/의학">건강/의학</option>
                <option value="스포츠">스포츠</option>
            <?php } elseif ($ca_name = '지역/국가') { ?>
                <option value="국가명">국가명</option>
                <option value="지역명">지역명</option>
            <?php } elseif ($ca_name='사회') { ?>
                <option value="정치/행정">정치/행정</option>
                <option value="경제/경영">경제/경영</option>
                <option value="국방/군사">국방/군사</option>
                <option value="사회안전/범죄/법률">사회안전/범죄/법률</option>
                <option value="교육">교육</option>
                <option value="직업">직업</option>
                <option value="종교">종교</option>
            <?php } elseif ($ca_name='자연') { ?>
            <option value="동물">동물</option>
            <option value="식물">식물</option>
            <option value="천체">천체</option>
            <option value="기후">기후</option>
            <option value="자연환경">자연환경</option>
            <?php } elseif ($ca_name='기계/교통/IT') { ?>
            <option value="기계/기기">기계/기기</option>
            <option value="교통">교통</option>
            <option value="전자통신/IT">전자통신/IT</option>
            <?php } elseif ($ca_name='기타') { ?>
            <option value="기타">기타</option>
            <?php } ?>

        </select>
    </div>
<?php } ?>