Access values of multiple checked boxes - php

Question

I want to access the values of dynamically created check boxes.
# $db = mysql_connect("abc", "abc", "");
mysql_select_db("abc");
$strSQL = "SELECT * FROM student";
$rs = mysql_query($strSQL);
$num_rows = mysql_num_rows($rs);
echo "<i style='color:#fff'> Number of Students = ".$num_rows."</i>";
$i=1;
while($r = mysql_fetch_array($rs)){
echo "<tr>";
echo "<td class='promotetabledata'>".$r[7]."</td>";
echo "<td class='promotetabledata'>".$r[6]."</td>";
echo "<td class='promotetabledata'><input type='checkbox' class='pr' value='".$r[7]."'/></td>"; /*dynamically created check boxes*/
echo "</tr>";
$i++;
}
The results are displayed in a promoteresults div using AJAX
<form id="promotionform" action="promotestudents.php" method="POST">
<div id="promoteresults">The results will show up here..!!
</div>
<div style=" position:relative; margin-top:10px; padding-left:44%;">
<button type="submit" class="button black">Promoted</a>
</div>
</form>
When the promoted button is clicked I want to get the selected records and update their value. To update the records, I need PHP. I can access the selected records in Javascript using
var selected = document.getElementsByClassName('pr').checked;
But how do I get the checked records in the HTML form and their values in PHP
The AJAX call with Javascript
function getpromotestudents()
{
//alert("hi");
var xmlhttp;
var select1 = document.getElementById('promotefacultyselect1');
var facutlyselect = select1.options[select1.selectedIndex].value;
var select2 = document.getElementById('promotedepartmentselect1');
var deptselect = select2.options[select2.selectedIndex].value;
var select3 = document.getElementById('promotecourseselect1');
var courseselect = select3.options[select3.selectedIndex].value;
var select4 = document.getElementById('promoteyearselect1');
var yearselect = select4.options[select4.selectedIndex].value;
var select5 = document.getElementById('promotesemselect1');
var semselect = select5.options[select5.selectedIndex].value;
var the_data = 'faculty='+facutlyselect+' &dept='+deptselect+' &course='+courseselect+' &year='+yearselect+' &sem='+semselect;
if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
/*
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("searchresults").innerHTML=xmlhttp.responseText;
}
}*/
xmlhttp.open("POST", "getpromotestudents.php", true); // set the request
xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); // adds a header to tell the PHP script to recognize the data as is sent via POST
xmlhttp.send(the_data); // calls the send() method with datas as parameter
// Check request status
// If the response is received completely, will be transferred to the HTML tag with tagID
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {
document.getElementById("promoteresults").innerHTML = xmlhttp.responseText;
}
}
}

Answer 1

<td class='promotetabledata'><input type='checkbox' name='pr[]' value='".$r[7]."'/></td>
This is the PHP code I finally wrote to access all the checkboxes, and perform the required operations on the selected ones.
<?php
$checkbox = $_POST['pr'];
foreach($checkbox as $value){
if(isset($checkbox)){
echo '<script>alert("'.$value.'")</script>';
}
}
?>

Answer 2

Give each of the checkbox name property like this
<input type='checkbox' class='pr' value='8' name='chk[]'/>
Than in the php you can get them as follows
<?php
$chkbox = $_POST['chk'];
foreach($chkbox as $a => $b){
echo $chkbox[$a];
}
?>

Answer 3

Set each check box's name property to pr[], as in:
echo "<input type='checkbox' class='pr' name='pr[]' value='".$r[7]."'/>";
Then, the first checkbox will be at $_POST['pr'][0], the second at $_POST['pr'][1] and so on.