Selecting contacts for sending mail to multiple recipients(check all check boxes on checking one checkbox and transfer their values to a textarea)

this is main checkbox to check all textboxes under it. after checking this checkbox, all sendto[] checkboxes will be checked and their values will be copied to textarea

<input type="checkbox" name="sendto[]" id="sendto[]" value="all" onClick="check(this.value)">

php code to add multiple check boxes fetched from database

<?php

$result = mysql_query("SELECT * FROM tbl_user");

while($row = mysql_fetch_array($result)) {

?>

<input type="checkbox" name="sendto[]" id="sendto[]" value="<?php echo $row['email']; ?>" onClick="addto(this)">

<?php } ?>

textarea to add multiple email ids

<textarea name="to" cols="29" rows="" id="to"  required class="span121"  style="width:386; height:71px;" ></textarea>

javascript function to add or remove all checkboxes' value to textarea

<script>

function check(val) {

var cnt = 5; //total number of checkboxes. can give value of php's mysql_num_rows variable

if(val=="all") {

var toval = '';

if(document.getElementsByName('sendto[]')[0].checked) {

for(i=1;i<=cnt;i++) {

document.getElementsByName('sendto[]')[i].checked=true;

toval = toval + $("#to").val() + document.getElementsByName('sendto[]')[i].value + ';';

}

$("#to").val(toval);

} else {

for(i=1;i<=cnt;i++) {

document.getElementsByName('sendto[]')[i].checked=false;

$("#to").val('');

}

}

}

}

</script>

javascript function to add or remove particular checkbox's value to textarea

<script>

function addto(objChkbx) {

var toval = $("#to").val() + objChkbx.value + ';';

if(objChkbx.checked) { $("#to").val(toval); }

else{ document.getElementById('to').value = document.getElementById('to').value.replace(objChkbx.value+';',""); }

}

</script>