//--- form inputan
<?php
$hobi=array('olahraga'=>'Olahraga','bacabuku'=>'Baca Buku','internetan'=>'Internatan');
$i=0;
foreach($hobi as $val=>$text)
echo "<tr><td>".($i++==0?'Hobi':'')."</td><td><input type='checkbox' name='hobi[]' value='{$val}'>{$text}</td></tr>";
?>


//-- proses, hasil yang diterima
$hobi=implode(" ",$_POST['hobi']);