How to validate the tetxbox in php only-CodePudding

I want to validate my textbox which must be required to fill in, but my code does not run after i press the submit button, the warning does not come out if i submit with black textbox? How to improve the code by only php?

<?php

if (isset($_POST['submit']))
{
    $vperson = $_POST['person'];
    if (empty($vperson))
    {
        $sperson = "Person is required";
    }
    else 
    {
        $sperson = "";
    }
}

?>
<html>
<head>
    <h1>Members</h1>
       <style>
        .error {color: #FF0000;}
        </style>
</head>
<body>
    <form method="post" action="members.php">
        <table border="1">
            <tr>
                <td >Number of Person</td>
                <td align="center"><input type="text" name="person" ><span ><?php echo $sperson;?></span></td>
            </tr>
            <tr>
                <th colspan="2" align="right"><input type="submit" name="submit" value="submit"></th>
              </tr>
        </table>
    </form>

CodePudding user response：

Your form action is action="members.php" so this is where you should place your validation. Generally speaking, for such validation I would use ajax request. If for some reason you can't use JavaScript, try return GET variable with error:

Your main file (lets say it is index.php)

<html>
<head>
    <h1>Members</h1>
    <style>
        .error {
            color: #FF0000;
        }
    </style>
</head>
<body>
<form method="post" action="members.php">
    <table border="1">
        <tr>
            <td>Number of Person</td>
            <td align="center">
                <input type="text" name="person">
                <span >
                    <?php echo $_GET['error'] === 'unknown_person' ? 'Person is required' : ''; ?>
                </span>
            </td>
        </tr>
        <tr>
            <th colspan="2" align="right"><input type="submit" name="submit" value="submit"></th>
        </tr>
    </table>
</form>

Add this at the top of your members.php (replace index.php with your file name)

<?php
if (empty($_POST['person'])) {
    header('Location: index.php?error=unknown_person');
}