1 .

    foreach ($all_wechat as $k => $v) {
        if (in_array($v, $select_wechat)) {
            unset($all_wechat[$k]);
        }
    };


    2.

    $r = array_filter($arr1, function ($v) use ($arr2) {
        return !in_array($v, $arr2);
    });


    缩写:

foreach ($all_wechat as $k => $v) if (in_array($v, $select_wechat)) unset($all_wechat[$k]);