rendered paste body <input type="checkbox" id="interest1" name="interest[1]" value="1" <?php if(in_array(1,$_POST[interest])) echo 'checked';?>> 1<br>
<input type="checkbox" id="interest2" name="interest[2]" value="2"<?php if(in_array(2,$_POST[interest])) echo 'checked';?>> 2<br>
<input type="checkbox" id="interest3" name="interest[3]" value="3"<?php if(in_array(3,$_POST[interest])) echo 'checked';?>> 3 <br>
<input type="checkbox" id="interest-checkall" name="interest[4]" value=""onclick='checkAllThree("interest1","interest2","interest3",this.id)'> All of the Above<br>
<?php $extra[]=$_POST[interest];
print_r( $_POST[interests]);?>