ต้องการใช้เงื่อนไข วันที่ระหว่างกับ Datatable (DateBetween) ทำอย่างไรครับ

<?php
require('../../connect.php');

$table = 'record';
$primaryKey = 'id';


// รับค่า ID จาก admin.php
if(isset($_GET['term'])){
    $term = mysqli_real_escape_string($con, $_GET['term']);
} else {
    $term = '';
}

if(isset($_GET['dp'])){
    $dp = mysqli_real_escape_string($con, $_GET['dp']);
} else {
    $dp = '';
}

if(isset($_GET['startdate'])){
    $startdate = mysqli_real_escape_string($con, $_GET['startdate']);
} else {
    $startdate = '';
}

if(isset($_GET['enddate'])){
    $enddate = mysqli_real_escape_string($con, $_GET['enddate']);
} else {
    $enddate = '';
}


$columns = array(
    array( 'db' => 'id', 'dt' => 0 ),
	array( 'db' => 'classroom', 'dt' => 1 ),
    array( 'db' => 'period', 'dt' => 2 ),
    array( 'db' => 'subject', 'dt' => 3 ),
    array( 'db' => 'teacher', 'dt' => 4 ),
    array( 'db' => 's-all', 'dt' => 5 ),
    array( 'db' => 's-in', 'dt' => 6 ),
	array(
        'db'        => 'img',
        'dt'        => 7,
        'formatter' => function( $d, $row ) {
            return '
            <img src="upload/lfh/'.$d.'" width="300">';
        }),
        array(
            'db'        => 'id',
            'dt'        => 8,
            'formatter' => function( $d, $row ) {
                return '
                <button type="button" class="btn btn-sm btn-danger" data-toggle="modal" data-target="#DeleteR" data-whatever="'.$d.'"> <i class="fas fa-trash"></i> ลบ </button>';
            })
);

$sql_details = array(     
    'user' => $user,
    'pass' => $passwd,
    'db'   => $db,
    'host' => $host
    
    );


require( '../../datatable/ssp.class.php' );

// เงิ้อนไข
$t = "term = '$term'"; 
$sd = "startdate = '$startdate'"; 


$str = $t . ', ' . $sd;
$arr = explode(', ', $str);
$where = array_values(array_filter($arr, 'strlen'));

echo json_encode(
	SSP::complex($_GET, $sql_details, $table, $primaryKey, $columns, $where)
);
?>