TESTING

<script type="text/javascript" src="jquery-1.4.4.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
    $('.check:button').toggle(function(){
        $('input:checkbox').attr('checked','checked');
        $(this).val('uncheck all');
    },function(){
        $('input:checkbox').removeAttr('checked');
        $(this).val('check all');
    })
});
</script>

<form name=coba action='' method=post>
  <input type="button" class="check" value="check all" /><br>

   <input type="checkbox" name="coba[]" value="saya"> Saya <br>
   <input type="checkbox" name="coba[]" value="kamu"/> Kamu <br>
   <input type="checkbox" name="coba[]" value="dia"/> Dia<br>

    <input type="submit" value="kirim" name="kirim">
</form>
<?php
    if($_POST['kirim']){

        $data=$_POST['coba'];
        foreach($data as $value){
            echo $value."<br>";
        }
    }
    else {echo "gagal dikirim";};

?>