Php 在一个数组上循环并检查元素是否存在于另一个数组中

我有两个数组，第一个是

$practice_areas = array(
    array(
        "id" => 1, 
        "name" => "Administrative",
        "form_id" => 1
    ),
    array(
        "id" => 2,
        "name" => "Admiralty & Maritime",
        "form_id" => 1
    ),
    array(
        "id" => 3,
        "name" => "Agricultural",
        "form_id" => 1
    ),
    array(
        "id" => 4,
        "name" => "Alternative Dispute Resulution",
        "form_id" => 1
    ),
    array(
        "id" => 5,
        "name" => "Antitrust & Trade Regulation",
        "form_id" => 1
    ),
    array(
        "id" => 6,
        "name" => "Appellate Practice",
        "form_id" => 1
    )
);

第二个是

$selected\u id

$selected_id = array(
    array(
        "id" => 1,
        "lawyer_id" => 2,
        "practice_area_id" => 3
    ),
    array(
        "id" => 2,
        "lawyer_id" => 2,
        "practice_area_id" => 4
    )
);

这是我目前的代码：

<label>Practice area(s) *</label>
<select id="practice_areas" multiple="multiple" name="practice_areas[]">
    <option value="" selected="selected"></option>
<?php foreach($practice_areas as $practice_area) {?>
    <option value="<?php $practice_area['id'] ?>" <?php ($selected_id->practice_area_id == $practice_area['id']) ? 'selected="selected"' : ''; ?>><?php $practice_area['name'] ?></option>
<?php } ?>
</select>

我得到了这个结果

$selected_id = array(
    array(
        "id" => 1,
        "lawyer_id" => 2,
        "practice_area_id" => 3
    ),
    array(
        "id" => 2,
        "lawyer_id" => 2,
        "practice_area_id" => 4
    ),
    true,
    true
);

---

你可以这样做：

练习区*
请直接添加代码，不要将其作为图像添加。
只需尝试此
selected=”“
@devpro这不是因为$selected\u id是数组，您使用的是哪个php版本？我所做的是创建新的数组。我在回答中添加了一个eval.in链接，这样您就可以看到它是有效的。您在问题中添加的编辑内容没有意义。该输出与代码不对应。请注意，循环更改$is_selected，而不是$selected_id。我认为您混淆了它们。无论如何，请检查由生成的输出。
$selected_id = array(
    array(
        "id" => 1,
        "lawyer_id" => 2,
        "practice_area_id" => 3
    ),
    array(
        "id" => 2,
        "lawyer_id" => 2,
        "practice_area_id" => 4
    ),
    true,
    true
);