Inserting data to a database would be possible by using SQL statements, specifically the INSERT command. Data can be entered  into the database using insert query into the function, here is simple line of code that will create a database using insert query.

Database connection:-

<?php
	$servername = "localhost";
	$username = "root";
	$password = "";
	$dbname = "shopping_db";

    // Create connection
 $conn = new mysqli($servername, $username, $password, $dbname);
    // Check connection
 if ($conn->connect_error) 
    {
    die("Connection failed: " . $conn->connect_error);
    } 

   else
    echo "connection sucessfuly";
?>

Inserting values to the database using php code:-

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") 
{
	if (isset($_POST['username']) && ($_POST['email']) && ($_POST['password'])) 
	{
	     // collect value of input field
	     $username = $_REQUEST['username']; 
	     $email = $_REQUEST['email']; 
	     $password = $_REQUEST['password']; 
	     $sql = "SELECT * FROM details where email = '$email'";
    	     $result = $conn->query($sql);
             if ($result->num_rows == 1)
                {
              echo "<script type ='text/javascript'> alert ('This email is already registered')</script>";
    		}

             else{
	        $sql1 = "INSERT INTO details(username,email,password) VALUES('$username','$email','$password')";            
                if ($conn->query($sql1) === TRUE) 
		  {
		    header('Location:php_loginform.php');
		  }
	        else{
	          echo "Error creating database: " . $conn->error  
                    }
                  }  
	}
}

?>