Checkbox in PHP

Let's now learn how to work with checkbox in PHP. Let's create such a checkbox in our form:

html<form action="" method="GET">
  <input type="checkbox" name="flag">
  <input name="text">
  <input type="submit">
</form>

After submitting the form, $_GET of the checkbox will contain the string 'on' if the checkbox was checked and null if not:

html<?php
  var_dump($_GET['flag']); // 'on' or null
?>

Let's display something on the screen depending on whether the checkbox was checked or not:

html<?php
  if (!empty($_GET)) { // if the form was submitted
    if (isset($_GET['flag'])) { // if the checkbox is checked
      echo 'checked';
    } else {
      echo 'not checked';
    }
  }
?>