什么是组合函数而不是为每个数据重复它们的首选方法？ [关闭]

Question

I have created a set of functions to retrieve and display data from a database using a mysqli connection.

The functions basically do the same thing but for different fields of data requested. The functions below retrieve data from one table but i also need to get data from another table but would rather not just rewrite the same functions with a different query for each table.

For example the functions below display data for breakfast menu, i now need to create the evening menu which will use similar data but stored in a different table.

Im sure there is a much more efficient way of doing this but i'm inexperienced and would like some guidance or pointers towards a better solution. I am not asking for someone to do it for me, i want to learn for me myself with guidance :)

I guess the SQL query needs to be made dynamic where it selects a group and the function somehow needs to able to call the required group but i'm not sure how: function call would end up looking like this:

get_menu(breakfast_menu);

Where get_menu retrieves all the data and then the argument is where the group in this case breakfast_menu is selected.

function connect () {
    include_once ("config.php");
    static $conn;
    if ($conn===NULL){ 
        $conn = mysqli_connect ("$host", "$username", "$password", "$db");
    }
    return $conn;
}

function get_breakfast_menu() {
    $conn = connect();

        $query = "SELECT * FROM menuitems where `group`='breakfast_menu'";

            if ($result = mysqli_query($conn, $query)) {

            /* fetch associative array */
            while ($row = mysqli_fetch_assoc($result)) {

                    // data inside html goes here
                        }
                 }
            /* free result set */
            mysqli_free_result($result);
        }
        else{
    echo "ERROR: Could not able to execute $query. " . mysqli_error($conn);
}


        }

function get_sandwiches() {
            $conn = connect();

        $query = "SELECT * FROM menuitems where `group`='sandwiches'";

            if ($result = mysqli_query($conn, $query)) {

            /* fetch associative array */
            while ($row = mysqli_fetch_assoc($result)) {

                    // data inside html goes here

                }
            }
            /* free result set */
            mysqli_free_result($result);
        }
        else{
    echo "ERROR: Could not able to execute $query. " . mysqli_error($conn);
}

        }

function get_lunch_favourites() {
            $conn = connect();

        $query = "SELECT * FROM menuitems where `group`='lunch_favourites'";

            if ($result = mysqli_query($conn, $query)) {

            /* fetch associative array */
            while ($row = mysqli_fetch_assoc($result)) {

                    // data inside html goes here

                }
            }
            /* free result set */
            mysqli_free_result($result);
        }
        else{
    echo "ERROR: Could not able to execute $query. " . mysqli_error($conn);
}

        }


function get_light_bites() {
            $conn = connect();

        $query = "SELECT * FROM menuitems where `group`='light_bites'";

            if ($result = mysqli_query($conn, $query)) {

            /* fetch associative array */
            while ($row = mysqli_fetch_assoc($result)) {

                    // data inside html goes here
}
            }
            /* free result set */
            mysqli_free_result($result);
        }
        else{
    echo "ERROR: Could not able to execute $query. " . mysqli_error($conn);
}

        }


function get_sides() {
            $conn = connect();

        $query = "SELECT * FROM menuitems where `group`='sides'";

            if ($result = mysqli_query($conn, $query)) {

            /* fetch associative array */
            while ($row = mysqli_fetch_assoc($result)) {

                    // echo'd data inside html goes here
}
            }
            /* free result set */
            mysqli_free_result($result);
        }
        else{
    echo "ERROR: Could not able to execute $query. " . mysqli_error($conn);
}

        }

Answer 1

This should be pretty simple assuming that you are specifying $group and it's not user supplied data:

function get_menu($group) {
    $conn = connect();
    $query = "SELECT * FROM menuitems where `group`='$group'";
    //other code
}

If $group is user supplied ($_GET, $_POST etc..) then:

function get_menu($group) {
    $conn = connect();
    $query = "SELECT * FROM menuitems where `group`= :group";
    $stmt = $conn->prepare($query);
    $stmt->bind_param('group', $group);
    $stmt->execute();
    //other code
}

Call with: get_menu('breakfast_menu');

You would be better off refactoring into a class so that you can do other things like only call connect() once:

class myClass {
    private $conn;

    public function __construct() {
        $this->conn = $this->connect();
    }

    //other functions that use $this->conn
}

Also you really should separate the logic and the presentation, so maybe build a menu_template to display.