<form action="process.php" method="post">
  <input type="checkbox" name="myVariable" value="<?php echo $myVariable; ?>">
  <input type="submit" value="提交">
</form>

<?php
  if(isset($_POST['myVariable'])){
    $myVariable = $_POST['myVariable'];
  }
?>

<input type="checkbox" name="myVariable" value="<?php echo $myVariable; ?>" <?php if($myVariable == 'someValue') echo 'checked'; ?>>