$is_checked = isset($_POST['your_checkbox_name']) &&
              $_POST['your_checkbox_name'] == 'on';

短路计算将会注意，这样您就不会在your_checkbox_name未提交时访问它。

如果你的HTML页面是这样的:

<input type="checkbox" name="test" value="value1">

提交表单后，您可以检查它:

isset($_POST['test'])

or

if ($_POST['test'] == 'value1') ...

<?php

if(isset($_POST['nameCheckbox'])){
    $_SESSION['fr_nameCheckbox'] = true;
}

?>

<input type="checkbox" name="nameCheckbox" 

<?php 

if(isset($_SESSION['fr_nameCheckbox'])){
    echo 'checked'; 
    unset($_SESSION['fr_nameCheckbox']);
} 

?>

<?php

  if (isset($_POST['add'])) {

    $nama      = $_POST['name'];
    $subscribe = isset($_POST['subscribe']) ? $_POST['subscribe'] : "Not Checked";

    echo "Name: {$nama} <br />";
    echo "Subscribe: {$subscribe}";

    echo "<hr />";   

  }

?>

<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" method="POST" >

  <input type="text" name="name" /> <br />
  <input type="checkbox" name="subscribe" value="news" /> News <br />

  <input type="submit" name="add" value="Save" />

</form>

在BS3中

  <?php
                  $checked="hola";
                  $exenta = $datosOrdenCompra[0]['exenta'];
                  var_dump($datosOrdenCompra[0]['exenta']);
                  if(isset($datosOrdenCompra[0]['exenta']) and $datosOrdenCompra[0]['exenta'] == 1){

                      $checked="on";

                  }else{
                    $checked="off";
                  }

              ?>
              <input type="checkbox" id="exenta" name="exenta" <?php echo $checked;?> > <span class="label-text"> Exenta</span>

请注意isset($datosOrdenCompra[0]['exenta'])的用法

<form>
<input type="check" id=chk1 value="1">
<input type="check" id=chk2 value="1">
<input type="check" id=chk3 value="1">
</form>

当你检查chk2时，你可以看到如下值:

<?php
foreach($_POST as $key=>$value)
{
    if(isset($key))
        $$key=strip_tags($value);
}
insert into table (chk1,chk2,chk3) values ('','1','');
?>