您可以尝试此操作，如果字段中存在某些值，它将回显readonly，否则它将是空白字段，并显示required

<input type="text" name="login_password"   id="login_password"  placeholder="Desgination" value="<?php echo  $row["designation"]; ?>"  <?php if(trim($row["designation"]) !="") echo "Readonly"; else echo "required"; ?> >

我的2分钱！没有如果在html代码，一个坏习惯imho

$readonly = isset($row["designation"]) ? 'required' : '';

<input type="text" name="login_password" id="login_password" placeholder="Desgination" value="<?php echo $row["designation"] ?>" <?php echo $readonly; ?> required>

试试这个

<?php 
    if(!empty($row["designation"])){
       $condition = "readonly";
    else
      $condition = "required"; 
?>
<input type="text" name="login_password" id="login_password" placeholder="Desgination" value="<?php echo 
$row["designation"] ?>" <?php echo $condition; ?>>