php - 使用选择输入删除数据库中的对象后尝试获取非对象的属性

Question

I can choose and click 'Slett' to delete it from database

After deleting the rest doesnt come up

当我再次更新页面时，它们会出现...

作为错误，我得到“注意:删除后尝试获取非对象的属性”

我正在使用 PHP，一切正常，但删除后我没有选择输入中的选项。

这是我的代码，顺便说一句，我是 Stackoverflow 的新人

if(isset($_POST['endreProve']) || (isset($_POST['slettSpm']) )){

    if(isset($_POST['slettSpm'])){

        $spmId = $_POST['spmId'];

        $sql  = "DELETE FROM `alternativ` WHERE `SpormalId`= $spmId;";
        $sql .= "DELETE FROM `sporsmal` WHERE `sporsmal`.`SporsmalId` = $spmId"; 

      (mysqli_multi_query($conn, $sql));// {
    }  


     if(isset($_POST['endreProve'])){

            $id = $_POST['endreProve'];
            $id2 = explode('- ', $id);
            $_SESSION['proveId'] = $id2[1];


     }  



        $id = $_SESSION['proveId'];

 ?>


    <form style="padding-left: 30px; padding-top: 15px;" action="Rediger.php" method="POST">
    <div class='form-group row'> <div class='col-sm-12'>
    <h2><b> Prøve <?php echo $id ?> </b></h2>
            <label>Velg spørsmål:</label> 
            <select name="spmId">

<?php        

    $prove = "SELECT * FROM prove As p 
              INNER JOIN sporsmal As s ON p.ProveId = s.ProveId 
              INNER JOIN alternativ As alt ON s.SporsmalId = alt.SpormalId 
              WHERE p.ProveId = $id";

    $sql = "SELECT * FROM sporsmal WHERE ProveId = $id";

    $prove_result = $conn->query($sql);
    if($prove_result->num_rows > 0) {

        while($row = $prove_result->fetch_assoc()){


            $sporsmal = $row["Sporsmal"];
            $sporsmalId = $row["SporsmalId"];
            $svar = $row["Svar"];



                echo "<option  value='$sporsmalId'>$sporsmal</option>";

        }

    }        
                 ?>
         </select>
         <input type='submit' class='btn btn-primary btn-sm' name='endreSpm' value='Endre'>
         <input type='submit' class='btn btn-danger btn-sm' name='slettSpm' value='Slett'><br/><br/>

         <label><b>Legg til spørsmål</b></label><br/>
         <div class="form-group">
            <input type="text" class="col-sm-6" name="spm" placeholder="Spørsmål?" />
            <input type="text"  name="riktig" placeholder="svar" id="svar" readonly /><br/>

        </div>
        <div class="input-group">

            Skriv og velg riktig alternativ:
        <div class="input-group-prepend">
            <input type="text" id="alt1" name="alt1" placeholder="Alternativ1" id="1">
            <div class="input-group-text">
                <input type="radio" name="alt" value="1" onclick='bytteSvar(this.value)'>
            </div>
        </div>

        <div class="input-group-prepend">
            <input type="text"  id="alt2" name="alt2"  placeholder="Alternativ2"  id="2">
            <div class="input-group-text">
                <input type="radio" name="alt" value="2" id="alt2" onclick='bytteSvar(this.value)' >
            </div>
        </div>

        <div class="input-group-prepend">
            <input type="text" id="alt3" name="alt3" placeholder="Alternativ3">
            <div class="input-group-text">
              <input type="radio" name="alt" value="3" id="alt3"  onclick='bytteSvar(this.value)'>
            </div>
        </div>

        <div class="input-group-prepend">
            <input type="text" id="alt4" name="alt4"  placeholder="Alternativ4"  >
            <div class="input-group-text">
              <input type="radio" name="alt"  value="4" id="alt4" onclick='bytteSvar(this.value)'>
            </div>
        </div>
            <br/>
         <div class="input-group-prepend">
            <input type="text"  name="media"  placeholder="Media - /path/path"  >
            &nbsp<input type="submit"  name="leggTilSpm" value="Legg til" class="btn btn-success btn-sm">
        </div>
      </div>

      </div>
      </div>

<?php

}

Answer 1

在为选择列表创建选项的代码部分中，您使用的查询引用名称为 $id 的变量。当您删除行时，该值不会更新。您正在使用 session 中的旧值。即使您正在删除，也需要更新 session 中的值。

<?php
if (isset($_POST['endreProve']) || (isset($_POST['slettSpm']) )) {

    if (isset($_POST['slettSpm'])){

        $spmId = $_POST['spmId'];

        $sql  = "DELETE FROM `alternativ` WHERE `SpormalId`= $spmId;";
        $sql .= "DELETE FROM `sporsmal` WHERE `sporsmal`.`SporsmalId` = $spmId";

        (mysqli_multi_query($conn, $sql));
    }

    // !!! This is left out when you delete
    if (isset($_POST['endreProve'])){
        $id = $_POST['endreProve'];
        $id2 = explode('- ', $id);
        $_SESSION['proveId'] = $id2[1];
    }

    // !!! old session value is used instead, which refers to an deleted entry
    $id = $_SESSION['proveId'];

?>