[php] Getting checkbox values on submit

//retrive check box and gender value
$gender=$row['gender'];
$chkhobby=$row['chkhobby'];
<tr>
    <th>GENDER</th>
    <td>
            Male<input type="radio" name="gender" value="1" <?php echo ($gender== '1') ?  "checked" : "" ;  ?>/>
            Female<input type="radio" name="gender" value="0" <?php echo ($gender== '0') ?  "checked" : "" ;  ?>/>

    </td>
</tr>
<tr>
    <th>Hobbies</th>
    <td>
        <pre><?php //print_r($row);

            $hby = @explode(",",$row['chkhobby']);
            //print_r($hby);
        ?></pre>
        read<input id="check_1" type="checkbox" name="chkhobby[]" value="read" <?php if(in_array("read",$hby)){?> checked="checked"<?php }?>>
        write<input id="check_2" type="checkbox" name="chkhobby[]" value="write" <?php if(in_array("write",$hby)){?> checked="checked"<?php }?>>
        play<input id="check_4" type="checkbox" name="chkhobby[]" value="play" <?php if(in_array("play",$hby)){?> checked="checked"<?php }?>>


    </td>
    </tr>
//update
$gender=$_POST['gender'];
$chkhobby = implode(',', $_POST['chkhobby']);