表單提交后如何用php顯示錯誤消息

Question

大家好，我正在用 php 構建一個項目，我想在使用 php 提交的表單上顯示錯誤消息，但問題是我無法做到我的頁面重新加載並且消息不顯示。 下面我粘貼代碼，請幫助我如何做到這一點。

表格部分

<form method="post" action="" id="contact_form">
                      <div class="form-row mt-3">
                        <div class="col">
                          <div class="form-group input-group">
                            <input type="text" class="form-control" name="con_first_name" placeholder="Enter your first name">
                            <span><?php echo $err_fname; ?></span>
                          </div>
                        </div>
                        
                      </div>
                      
                      <div class="form-group"> 
                      
                        <button type="submit" name="con_submit" class="btn show_more con_submit">Submit</button>
                      </div> 
                    </form>

php代碼

if(isset($_POST['con_submit'])){
    
    
    
    // Posted form data 
    
    if(!empty($_POST['con_first_name'])){
        $err_fname = "First name cannot be empty";
    }else{
        $fname = htmlentities(strip_tags(mysqli_real_escape_string($con, $_POST['con_first_name'])), ENT_QUOTES, 'UTF-8');
    }
    
    
    
}

Answer 1

我會用會話來做！

session_start();
if(isset($_POST['con_submit'])){
    
    // Posted form data 
    if(!empty($_POST['con_first_name'])){
        $err_fname = "First name cannot be empty";
        $_SESSION['form_error'] = $err_fname;
    }else{
        $fname = htmlentities(strip_tags(mysqli_real_escape_string($con, $_POST['con_first_name'])), ENT_QUOTES, 'UTF-8');
    }
     
}

然后你想展示它的地方：

if(isset($_SESSION['form_error'])){
    echo $_SESSION['form_error'];
    unset($_SESSION['form_error']);
}

Answer 2

使用此代碼

if(isset($_POST['con_submit'])){
    if(empty($_POST['con_first_name'])){
        $err_fname = "First name cannot be empty";
    }else{
        $fname = htmlentities(strip_tags(mysqli_real_escape_string($con, $_POST['con_first_name'])), ENT_QUOTES, 'UTF-8');
    }
}

Answer 3

你可以像這樣使用會話

session_start();
if(isset($_POST['con_submit'])){
    
    // Posted form data 
    if(empty($_POST['con_first_name'])){
        $err_fname = "First name cannot be empty";
        $_SESSION['form_error_name'] = $err_fname;
    }else{
        $fname = htmlentities(strip_tags(mysqli_real_escape_string($con, $_POST['con_first_name'])), ENT_QUOTES, 'UTF-8');
    }
     
}

if(isset($_SESSION['form_error_name'])){
    echo $_SESSION['form_error_name'];
    unset($_SESSION['form_error_name']);
}

session 是安全的，每次發布它都會設置 session，然后它將刪除設置為 session 的值並取消設置 session。