mysqli Connect, Insert and Query data

// Build Connection with database.
$con = mysqli_connect("localhost","hkc","123","test_db");

// Database Connection checking with error numbers
if(mysqli_connect_error()){
        echo "Connection Error Number is : ".mysqli_connect_errno();
    }

// Specify values for enjoined fields of destination table.
Type 01 : $insert = "INSERT INTO test_table(name,roll,created_date) VALUES('Hasib',4153,NOW())";
Type 02 : $insert = "INSERT INTO test_table VALUES(null,'romel',4160,NOW())";

//Built Connection and send data into fields.
mysqli_query($con,$insert);

// Create Query
$query = mysqli_query($con,"SELECT * FROM test_table");

// To get few info by your query
print_r($query)

// Object oriented using this operator
$query->num_rows;                                 [**num_rows found from print_r($query); ]

// Fetch data row by row, by using while loop
while ($row = mysqli_fetch_array($query,MYSQLI_ASSOC)) {
        ?>
        <tr>
            <td><?php echo $row['id']; ?></td>
            <td><?php echo $row['name']; ?></td>
            <td><?php echo $row['roll']; ?></td>
            <td><?php echo $row['created_date']; ?></td>
        </tr>
        <?php
    }