how to send multiple parameters using php ajax

I am positive there are better ways, but currently, if I want to pass multiple parameters, I do something like this:

"someFunc.php?param=" + var1 + "|" + var2 + "|" + var3

And in PHP:

$var1 = explode('|', $_GET['param'])[0];
$var2 = explode('|', $_GET['param'])[1];
$var3 = explode('|', $_GET['param'])[2];

It's rather "quick and dirty", but it works :)

To achieve your goal of using an onclick event handler in a more correct manner you might find the following helpful.

The initial PHP is (virtually) unchanged other than some code formatting for legibility so if there are errors there then they were there before ;-)

$connected = mysqli_connect("localhost", "root", "", "web");
if( isset( $_GET['t'], $_GET['p'], $_GET['q'] ) ){

    $idd = $_GET['p'];
    $tit = $_GET['q'];
    $typ = $_GET['t'];

    if( '$typ' == 'accept') {

        $sql = "INSERT INTO coursestudent (stuID, cTitle) VALUES ('$idd', '$tit')";
        $result = mysqli_query($connected,$sql); 

        $sql2 = "DELETE FROM studentrequest WHERE sID = '$idd' AND cTitle = '$tit' AND tID = '1111'";
        $result2 = mysqli_query($connected,$sql2);

    } else { 
        $sql2 = "DELETE FROM studentrequest WHERE sID = '$idd' AND cTitle = '$tit' AND tID = '1111'";
        $result2 = mysqli_query($connected,$sql2);
    }
}

Every element in the HTML that has an ID attribute MUST have a unique ID to be considered valid and to allow correct targeting of the element programmatically - as the ID for each button was not really required they were removed. Instead though each button has dataset attributes assigned with the relevant pieces of information from the db - these dataset attributes will be accessed programmatically by the javascript function.

$teacherId = "1111";
$sqll = "SELECT cTitle, student.studentName, sID FROM student, studentrequest WHERE studentrequest.tID=$teacherId AND studentID=sID";

$res = mysqli_query( $connected, $sqll );
$acc = 'accept';
$rej = 'reject';

if( mysqli_num_rows( $res ) > 0 ){ 

    echo "<table id='students' border=1>
        <tr>
            <th>Title</th>
            <th> student name </th>
            <th> student ID </th>
            <th></th>
        </tr>";

    $row=0;

     while ( $row = mysqli_fetch_array( $res ) ){

        $title=$row['cTitle'];
        $sid=$row['sID'];


        echo "
        <tr>
            <td>{$row['cTitle']}</td>
            <td>{$row['studentName']}</td>
            <td>{$row['sID']}</td>
            <td><!--// Each button has `dataset` attributes //-->
                <input type='button' data-title='{$title}' data-sid='{$sid}' data-action='{$acc}' value='accept' />
                <input type='button' data-title='{$title}' data-sid='{$sid}' data-action='{$rej}' value='reject' />
            </td>
        </tr>"; 

        $row++;
    }
    echo " </table>";


} else {
    echo "<strong> no records found</strong>";
}

Rather than using inline event handlers the preferred way, in vanilla javascript, is to use something like the following to assign the event listeners to the relevant HTML elements.

To find all the correct buttons for which we wish to assign the ajax function ( as event handler ) using querySelectorAll provides a straightforward mechanism. If there are elements found that match the pseudo XPath expression iterate through the collection and assign a function to each element.

<script type='text/javascript'>
    var col = document.querySelectorAll( 'table#students td input[type="button"]' );
    if( col ){
        for( var n in col )if( col[ n ].nodeType==1 )col[ n ].addEventListener('click',function(e){
            var bttn = e.target;
            var action=bttn.dataset.action;
            var title=bttn.dataset.action;
            var sid=bttn.dataset.sid;

            var xhr = new XMLHttpRequest();
                xhr.onreadystatechange=function(response){
                    if ( xhr.readyState == 4 && xhr.status == 200 ) document.getElementById("fh5co-content").innerHTML = response;
                };
                xhr.open( 'GET', 'StudentRequest.php?q='+title+'&p='+sid+'&t='+action );
                xhr.send();

        }.bind( col[ n ] ), false );
    }
</script>

For the record the above is not tested ... hope it helps

get the value and pass it to // server script. For example

var test = document.getElementById('test').value;
var test2 = document.getElementById('test2').value;

 var queryString = "?test=" + test ;
 queryString +=  "&test2=" + test2;
 ajaxRequest.open("GET", "test.php" + queryString, true);
 ajaxRequest.send(null);