Dropdown selected value in a SESSION variable accross different pages doesn't persist

问题

On my list.php page, the user can choose a country from the drop-down to show the SQL server's data for the selection. On this selection, the user gets the option to update/edit the values on an edit.php page. When the user submits the changes on the edit.php page, they are redirected to a save.php page and then back to the initial list.php page. I was wondering if it's possible to use the SESSION variable to store the initial country selection so the user gets the same selection when redirected to list.php. I've tried to use session_start ();, but couldn't get it to work.

EDITED

This are pieces of my code:

Top of list.php:

<?php session_start(); ?>

Form:

<form name="frmname" id="frmid" action="list.php" method="POST" >
<h4>From: <input type="text" size="6" name="start_date" pattern="[0-9/]+" 
placeholder=" 00/00/0000" />
To: <input type="text" size="6" name="end_date" pattern="[0-9/]+" 
placeholder=" 00/00/0000" />
<select name="RegioSelect" onchange="this.form.submit();" ><option><?php echo $_SESSION['RegioSelect']; ?></option>

Dropdown populated by:

$query1 = "SELECT DISTINCT CountryRegionName FROM tKein23 ORDER BY CountryRegionName";
$stmt1 = $conn->query( $query1 );
while ($data = $stmt1->fetch(PDO::FETCH_ASSOC)){
    echo '<option value="'.$data['CountryRegionName'].'">';
    echo $data['CountryRegionName']; 
    echo "</option>";
}

Then I tried SESSION_START():

<h4><input type="submit" value="Show" name="Selection" />
</select>
</form>

<?php

    if(isset($_POST["RegioSelect"])){
        $_SESSION['RegioSelect'] = $_POST["RegioSelect"];
    }

Now, on other pages, I do get the $_SESSION['RegioSelect'] variable. On list.php, I get the variable in the drop-down but no submission.

回答1:

session_start() must come first, before any other ouput. Not only before html on your php script, but before any browser output.

PHP Documentation

To use cookie-based sessions, session_start() must be called before outputing anything to the browser.

<?php session_start(); ?>

<html>
    <body>
        ...
        ...
        <h4><input type="submit" value="Show" name="Selection" />
        </select>
        </form>

<?php

    if (isset($_POST["RegioSelect"]))
        $_SESSION['RegioSelect'] = $_POST["RegioSelect"];

回答2:

If the form is on the same page, make sure to move the

if (isset($_POST["RegioSelect"]))
    $_SESSION['RegioSelect'] = $_POST["RegioSelect"];

to the top - right below the session_start() and before the <html>

otherwise you have to reload the page first - which is probably not what you want

from there on you can also do redirects to other pages via header()

来源：https://stackoverflow.com/questions/46384283/dropdown-selected-value-in-a-session-variable-accross-different-pages-doesnt-pe

标签

php

html

sql-server

session-variables