Undefined array in php-CodePudding

Form code

<form action=<?=$_SERVER['PHP_SELF']?> method="POST" id="form1">
Enter length of password:<input type="text" name="length">
<input type="submit" value="Submit"/>

PHP code

    <?php 
    $length=$_POST['length']
    ?>

Error:

Undefined array key "length" in D:\XWAMP\htdocs\pg\index2.php on line 30

I'm writing both html and php in single file that's why it's happening but how to handle it?

CodePudding user response：

I assume the web page loads and you get the error. In this case, you haven't check whether the form is submitted. Before the form is submitted you also haven't added a name for your submit button.

if(isset($_POST['submit'])){
    $length = $_POST['length'];
}

This should solve your problem I suppose. A similar question was asked here: Check if form was submitted

CodePudding user response：

Various issues,

action=<?=$_SERVER['PHP_SELF']?> is open to XSS don't use it
To check if its POST request, use $_SERVER['REQUEST_METHOD'] === 'POST'
Always validate user input and respond in kind to the user

<?php
$errors = [];
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
   // validate length
   if (!isset($_POST['length'])) {
     $errors['length'] = 'Length is a required field';
   } else if (!is_numeric($_POST['length'])) {
     $errors['length'] = 'Length should be a number';
   } else if ($_POST['length'] < 1) {
     $errors['length'] = 'Length should be a >= then 1';
   } else if ($_POST['length'] > 1000) {
     $errors['length'] = 'Length should be a <= then 1000';
   }

   // no errors, do processing on length
   if (empty($errors)) {
      $length = $_POST['length'];

      // do something with $length
   }
} 
?>

<form action="" method="POST" id="form1">
  Enter length of password: 
  <input type="text" value="<?= isset($_POST['length']) ? htmlentities($_POST['length']) : '' ?>" name="length" required>
  <?= isset($errors['length']) ? '<div >'.$errors['length'].'</div>' : '' ?>
  
  <input type="submit" value="Submit"/>
</form>