Retaining checkbox status in post back data of form in PHP

Keep a checkbox selected after validation

For a sticky form, derive the checked attribute from submitted data instead of assuming the field will always be present.

$agreed = isset($_POST['agreed']);
$checked = $agreed ? ' checked' : '';

echo '<input type="checkbox" name="agreed" value="yes"' . $checked . '>';

This is the recommended starting pattern. The detailed examples below are retained for explanation, comparison and related variations.

Use the checkbox in above form and on submit the status of the Checkboxes are retained.

This tutorial is part of the series where we will try to understand how to retain value of every component of a form. You can read our main tutorial on how to retain value for component of a form here.

We will use php header redirection to post back the values to our main page where checkbox is present. We will call form page as first page and action or submitted page as second page. The form data will be received by second page and after validation it is supposed to complete all the processing and in case of error it will post back the form data back to form page by using query string through address bar.

We will use the example of two checkbox but same system can be extended to more than two or single checkbox in a form.

Here is the code of a form with two checkboxes

$t1=$_GET['t1'];
$t2=$_GET['t2'];

if($t1=="yes"){$t1v="checked";}
else{$t1v=="";}

if($t2=="yes"){$t2v="checked";}
else{$t2v=="";} 

echo "<form method=post action=pb-chk.php>
<input type=checkbox name=t1 value=yes $t1v> This is first checkbox<br>
<input type=checkbox name=t2 value=yes $t2v> This is second checkbox
<input type=submit value=Submit>";

To keep the second page simple we will keep only the redirection part. Here we have excluded the part which takes care if the form passes its validation and execute the actual script.

Inside the file pb-chk.php we receive the data using POST method and create the query string. ( GET method is used to receive data in Form page or pb-check.php page )
Here is the code of second page, pb-chk.php

$t1=$_POST['t1']; // receive form ( checkbox value) data using POST method
$t2=$_POST['t2'];
header ("Location: pb-check.php?t1=$t1&t2=$t2"); // redirect to First page or Form page

Difference between GET and POST method of Form submission
PHP Form Managing Radio button using PHP

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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AARON	04-01-2019
I have been searching the whole net for this and here I am with the true answer to my problem. Thank you!

Retaining checkbox value of a form after posting

Keep a checkbox selected after validation

Subhendu Mohapatra