php - 验证后为什么我的表单数据被清除

Question

我正在对我的 html 值进行 PHP 验证。但是当 PHP 验证时 失败，我返回页面，表单数据被清除。无论如何，有没有办法在 php 中保存并重新加载表单数据

php中的验证代码

<?php
    $firstname=$lastname=$contactno="";
    $firstnameErr=$lastnameErr=$contactnoErr="";
    
    if ($_SERVER['REQUEST_METHOD']== "POST") {
       $valid = true;
         
    /*FirstName Validation starts here*/     
     if(empty($_POST["fname"]))
    {
        $firstnameErr="*firstname is Required";
            $valid=false;
    }
    else
    {
    $firstname=test_input($_POST["fname"]);
     if (!preg_match("/^[a-zA-Z ]*$/",$firstname))
           {
           $firstnameErr = "&nbsp;&nbsp;Only letters and white space allowed"; 
           $valid=false;
           }    
    } 
    /*FirstName Validation Ends here*/   
       
       /*lastName Validation starts here*/   
       if(empty($_POST["lname"]))
       {
           $lastnameErr="*lastname is required";
           $valid=false;
       }
       else
       {
           $lastname=test_input($_POST["lname"]);
           if(!preg_match("/^[a-zA-Z ]*$/",$lastname))
           {
               $lastnameErr = "&nbsp;&nbsp;Only letters and white space allowed";
               $valid=false;
           }
       }
       /*LastName Validation Ends here*/     
        
    /*Contact No Validation starts here*/    
       if(empty($_POST["contact"]))
       {
           $contactnoErr="*Contact No. is required";
           $valid=false;
        }
        else
        {
            $contactno=test_input($_POST["contact"]);
             if(!preg_match("/^(\d[\s-]?)?[\(\[\s-]{0,2}?\d{3}[\)\]\s-]{0,2}?\d{3}[\s-]?\d{4}$/i",$contactno)) 
           {
            $contactnoErr="*Enter a valid contact no";
            $valid=false;
           }    
        }
       /*Contact No Validation Ends here*/
         
     //if valid then redirect
      if($valid){
          include 'database.php';
          echo '<META HTTP-EQUIV="Refresh" Content="0; URL=success.php">';    
        exit;
      }  
    }
    
    function test_input($data)
    {
         $data = trim($data);
         $data = stripslashes($data);
         $data = htmlspecialchars($data);
         return $data;
    }
    
    ?>

表单

<form method="post" action="<?php htmlspecialchars($_SERVER["PHP_SELF"]);?>">
        <label>Firstname<span class="error">*</span>:</label>
        <input type="text" name="fname"/>
        <span class="error"><?php echo $firstnameErr?></span><br />
        <br />
        <label>lastname<span class="error">*</span>:</label>
        <input type="text" name="lname"/>
        <span class="error"><?php echo $lastnameErr?></span><br />
        <br />
        <label>contactno<span class="error">*</span>:</label>
        <input type="text" name="contact"/>
        <span class="error"><?php echo $contactnoErr?></span>
        <br />
    <input style="margin:20px 20px 20px 250px;" type="submit" name="Submit" value="Submit"/>
</form>

Answer 1

您正在加载一个新表单(即使它与上次加载的表单相同)，并且您的任何输入都没有 value 属性。