Prefilling Text Fields in PHP

Prefilling input text box

<?php
 // Before PHP 7.0, 
 // use isset function to determine if the field contains value
 $fname = isset($_POST['fieldname']) ? $_POST['fieldname'] : '';
 
 // For PHP 7.0 or above, use null coalescing operator (??)
 $fname = $_POST['fieldname'] ?? '';
 
 // Encode html special characters (<, >, ', ", etc.)
 $fname = htmlspecialchars($fname);

?>
...
<input type="text" name="fieldname" value="<?php echo $fname; ?>" >
...

The value in text fields (such as hidden, password, time, datetime-local, color, email, url, number, etc. see form elements) is provided in the value attribute. However, the data there must be properly encoded with htmlspecialchars() function to get rid of dangerous characters such as ' or < or >. The code snippet in the preceding code expects the form to be submitted back to itself; thus, it extracts the current value of the text field from $_POST (it would work analogously with $_GET).

Prefilling Text Fields

<?php
 $uname = htmlspecialchars ($_POST['uname'] ?? '');
 $email = htmlspecialchars ($_POST['email'] ?? '');
 
?>
<form method="post" action="example.php">
 Name:<br>
 <input type="text" name="uname" value="<?=$uname?>"><br>

 Email:<br>
 <input type="email" name="email" value="<?=$email?>"><br>
 <input type="submit" name="submit" value="Submit">
</form>

If you want to use a default value for this form element, you just have to provide this default value instead of the empty string in the PHP code:

<?php
 //Guest if uname field is not set
 $uname = htmlspecialchars ($_POST['uname'] ?? 'Guest');

 //no@xy.z if email field is not set
 $email = htmlspecialchars ($_POST['email'] ?? 'no@xy.z');
 
?>
<form method="post" action="example.php">
 Name:<br>
 <input type="text" name="uname" value="<?=$uname?>"><br>

 Email:<br>
 <input type="email" name="email" value="<?=$email?>"><br>
 <input type="submit" name="submit" value="Submit">
</form>

Prefilling textarea (multiline text field)

With multiline text fields, almost the same approach as with single-line text fields and password fields can be used. The only difference is the location where to put the prefill value.

To preset the value of a textarea, print the value between the textarea tags:

<textarea cols="40" rows="5"
name="areafieldname">Enter your data here ...></textarea>

It belongs between <textarea> and </textarea>, as shown in the code.

Prefilling Multiline Text Fields

<?php
 $mtext = $_POST['mtext'] ?? '';
 $mtext = htmlspecialchars($mtext); 
?>
<form method="post" action="example.php">
Multiline text:<br>

<textarea cols="40" rows="5"
name="mtext"><?= $mtext ?></textarea>

<br>
<input type="submit" name="submit" value="submit">

If you want to provide a default value in the multiline text field (for example, “Enter your data here …”), provide this instead of the empty string in the PHP code:

<?php
 $mtext = $_POST['mtext'] ?? 'Enter your data here ...';
 $mtext = htmlspecialchars($mtext); 
?>
<form method="post" action="example.php">
Multiline text:<br>

<textarea cols="40" rows="5"
name="mtext"><?= $mtext ?></textarea>

<br>
<input type="submit" name="submit" value="submit">

Prefill Forms using Cookies

Another possibility is to prefill form values from cookies. This is quite useful when users enter their data into a form several times. So, when they visit a form on the site a couple of days later, the old data can be retrieved from the cookie.

The following code retrieves a value from the cookie that contains the field data.

Saving and Retrieving Form Data from Cookies

<?php
 if (isset($_POST['submit'])) {
  $uname = htmlspecialchars ($_POST['uname'] ?? '');
  $email = htmlspecialchars ($_POST['email'] ?? '');
  $mtext = htmlspecialchars ($_POST['mtext'] ?? '');

  // Save the form data in cookies when form is submitted
  setcookie('uname', $uname, strtotime ('+30 days'));
  setcookie('email', $email, strtotime ('+30 days'));
  setcookie('mtext', $mtext, strtotime ('+30 days'));
 }
 else {
  // Form not submitted
  // Retrieve data from cookies (if exist)
  $uname = $_COOKIE['uname'] ?? '';
  $email = $_COOKIE['email'] ?? '';
  $mtext = $_COOKIE['mtext'] ?? '';  
 }
?>
<form method="post" action="example.php">
 <p>Name:
 <input type="text" name="uname" value="<?=$uname?>"></p>

 <p>Email:
 <input type="email" name="email" value="<?=$email?>"></p>
 
 <p>Comments:<br>
 <textarea name="mtext" rows="5" cols="40"><?=$mtext?></textarea></p>

 <p><input type="submit" name="submit" value="Submit"></p>
</form>

Processing Forms in PHP: