将选中的复选框添加到PHP变量中，然后我可以直接在下面查看

Question

I want to put all values from selected checkboxes into its own PHP variable. These checkboxes have their values generated by PHP/SQL. This same variable has to be shown in a simple <div> below the dropdown boxes. I am also using Bootstrap Multiselect Plugin. But I get a null value from my var_dump() test.

here is what I have attempted so far:

<form id="menu1" method="POST" action="index.php">
    <h2>Area Code</h2>
    <select id="multi-select1" name="multi_select1[]" multiple="multiple">
        <?php
            //The query asking from our database
            $areaCodeSQL = "SELECT ac.Number AS `AreaCode`, ac.Name AS `AreaName`
                            FROM `AreaCodes` ac";                                                               //SQL query: From the table 'AreaCodes' select 'Number' and put into 'AreaCode', select Name and put into 'AreaName'

            $areaCodeResults = $conn->query($areaCodeSQL);                                                      // put results of SQL query into this variable

            if ($areaCodeResults->num_rows > 0) {                                                               // if num_rows(from $results) is greater than 0, then do this:
                // output data of each row
                            foreach($areaCodeResults as $areaCodeResult)                                        //for each item in $areCodeResults do this:
                                {
                                    $areaNameAndCode =  $areaCodeResult['AreaCode'] ." ". $areaCodeResult['AreaName'];  //get AreaCode and AreaName from query result and concat them
                                    $areaName = $areaCodeResult['AreaName'];                                    // get AreaName
                                    $areaCode = $areaCodeResult['AreaCode'];                                    //get AreaCode

                                    ?><option class="menuoption1" name="menuAreaCode" value="<?php echo $areaCode ?>"  ><?php echo $areaNameAndCode; ?></option><?php  //Create this option element populated with query result variables
                                }
            } 
            $result = $_POST['multi_select1'];                   
        ?>
    </select>   
</form>
<div id="showResults1"><?php var_dump($result) ?></div>

I can however accomplish what I want to do by using jQuery but I want to be able to send those values to a database and my tutor wants them to be in PHP variables. I know I can use AJAX to send them to my database but this is what my tutor wants instead. I don't know if I am on the right track, so any help is greatly appreciated

Answer 1

At the very first run you wont read anything from that POST variable, so handle it. Try this code, it should work:

<form id="menu1" method="POST">
    <h2>Area Code</h2>
    <select id="multi-select1" name="multi_select1[]" multiple="multiple" action="index.php">
        <?php
            //The query asking from our database
            $areaCodeSQL = "SELECT ac.Number AS `AreaCode`, ac.Name AS `AreaName`FROM `AreaCodes` ac";                                                               //SQL query: From the table 'AreaCodes' select 'Number' and put into 'AreaCode', select Name and put into 'AreaName'
            $areaCodeResults = $conn->query($areaCodeSQL);                                                      // put results of SQL query into this variable

            if ($areaCodeResults->num_rows > 0) {                                                               // if num_rows(from $results) is greater than 0, then do this:
            // output data of each row
                foreach($areaCodeResults as $areaCodeResult) { ?>
                    <option class="menuoption1" name="menuAreaCode" value="<?php echo $areaCodeResult['AreaCode'] ?>"  ><?php echo $areaCodeResult['AreaCode'] ." ". $areaCodeResult['AreaName']; ?></option>
            <?php } ?>
    </select>   
    <input type="submit" value="Send" />
</form>
<div id="showResults1">
    <?php 
    $result = isset($_POST['multi_select1']) ? $_POST['multi_select1'] : [];
    var_dump($result);
    ?>
</div>