How to use array_intersect inside foreach in PHP, MySQL

Question

I'm trying to loop a table by comparing the results that I get from another table but it seems to be skipping the null index value.

What I want to get from the result is if one of the value of $a can be found on $b, it should echo the loop that it is associated or rather the index of that array.

       <ol>
            <?php
            $questions = db_query("SELECT * FROM tbl_questions");
            while ($quests = $questions->fetch_assoc()) {
                $b[] = $quests['question_id'];
                $comp = db_select("SELECT * FROM tbl_votes WHERE `user_id` = $userids");
                foreach($comp as $compare){
                    $check[] = $compare['question_id'];
                }
                $a = array_intersect($b, $check);
                if($a){
                    echo "<li><a class='qstyle' href='questions/".$quests['question_id'].".php'>".$quests['question_title']."</a></li>";
                }
                elseif($quests['question_live'] == 1){
                        echo "<li><strong><a class='qstyle' href='vote_page.php?var=".$quests['question_id']."'>".$quests['question_title']."</a></strong></li>";
                }
                elseif($quests['question_live'] == 0){
                    echo "<li style='color:#968c8d'>".$quests['question_title']."</li>";
                }                       
            }
            ?>
        </ol>

harrrrrrry · Accepted Answer · 2015-09-29 15:31:24Z

you questions array loop should be closed before you intersect with your $check, or you cant get the total questions.

Also, you need to alter your logic to show the difference. Based on your requirement, I dont think you should use array_intersect.

Actually if you use print_r($b); after $b[] = $quests['question_id']; you will find your $b is not what you expect.

Try this:

<ol>
            <?php
            $questions = db_query("SELECT * FROM tbl_questions");
            while ($quests = $questions->fetch_assoc()) {
                $b[$quests['question_id']] = $quests;
            }
            $comp = db_select("SELECT * FROM tbl_votes WHERE `user_id` = $userids");
            foreach($comp as $compare){
                $check[] = $compare['question_id'];
            }
            foreach($b as $qid=>$quest){
                if(in_array($qid, $check)) echo "<li><a class='qstyle' href='questions/".$qid.".php'>".$quest['question_title']."</a></li>";
                elseif($quest['question_live'] == 1) echo ...;
                elseif($quest['question_live'] == 0) echo ...;
            }
            ?>
        </ol>

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