PHP从MySQL转mysqli后，基于explode/implode的复选框回显失效求助

Hey there, let's troubleshoot why your checkbox checked states stopped working after switching to mysqli. I've gone through your code and spotted a few key issues that are likely causing the problem:

1. Variable Scope Issue with Database Connection #

Your GetCheckboxes function uses $con directly, but if this connection variable is defined in koneksi.php (a separate file), the function doesn't have access to it by default. Unlike the old mysql_* functions which used the last open connection automatically, mysqli requires you to explicitly pass the connection or make it available in the function's scope.

2. Missing Quotes for Array Keys #

When you access $r[user_course], you're using an unquoted string as an array key. While PHP allows this in non-strict mode, it can lead to unexpected behavior (PHP treats it as a constant first, falling back to a string only if no constant exists). This might be preventing you from correctly retrieving the stored checkbox values from the users table.

3. Lack of Error Checking #

You're not validating if your mysqli queries succeed. If a query fails (e.g., wrong table name, connection glitch), you won't get any feedback, making it hard to debug why no checkboxes are checked.

Fixed Code Implementation #

First, Update the GetCheckboxes Function

Pass the database connection as a parameter (better practice than relying on global scope for maintainability):

function GetCheckboxes($con, $table, $key, $Label, $Nilai='') {
    // Add error checking for the query
    $s = "SELECT * FROM $table ORDER BY id_course";
    $r = mysqli_query($con, $s);
    if (!$r) {
        die("Query failed: " . mysqli_error($con));
    }

    $_arrNilai = explode(',', $Nilai);
    $str = '';
    while ($w = mysqli_fetch_array($r, MYSQLI_ASSOC)) { // Use associative array explicitly
        // Clean up value check with in_array()
        $_ck = in_array($w[$key], $_arrNilai) ? 'checked' : '';
        $str .= "<div>
            <input type='checkbox' name='".$key."[]' value='$w[$key]' $_ck> 
            $w[$Label]
        </div>";
    }
    return $str;
}

Then, Update the Profile Page Code

Fix array key quotes, add session start, and pass the connection to the function:

// Always start session before accessing $_SESSION
session_start();
include 'koneksi.php'; // Include your connection file

$sql = mysqli_query($con,"SELECT * FROM users WHERE user_email='{$_SESSION['emailuser']}'");
// Verify query success and user existence
if (!$sql || mysqli_num_rows($sql) === 0) {
    die("User not found or query failed: " . mysqli_error($con));
}
$r = mysqli_fetch_array($sql, MYSQLI_ASSOC); // Use associative array for clarity

// Render checkboxes, pass $con as the first parameter
echo "<label><h4>Course you are applying for:</h4></label>";
$d = GetCheckboxes($con, 'main_course', 'course_seo', 'course_name', $r['user_course']);
echo $d;

Additional Notes #

• Don't forget session_start() at the top of any page using $_SESSION variables (I added this since it was missing in your original code).
• Using MYSQLI_ASSOC instead of MYSQLI_BOTH keeps your code cleaner by only returning associative keys, avoiding confusion with numeric indexes.
• in_array() is a more straightforward alternative to array_search() for checking if a value exists in an array.

Content of the question comes from Stack Exchange, question author: putu mega