update_ratings.php

<?php
include("connect.php");


$choice = $_POST['choice'];
$image1Id = $_POST['image1Id'];
$image2Id = $_POST['image2Id'];


if ($choice === 'first_one') {
    first_one($conn, $image1Id,$image2Id);
} elseif ($choice === 'second_one') {
    second_one($conn, $image1Id,$image2Id);
}

function first_one($conn, $image1Id,$image2Id) {
        $image1Rating = getImageRating($conn, $image1Id);
        $image2Rating = getImageRating($conn, $image2Id);

        $kFactor = 50;
               
        $expectedScore1 = getExpectedScore($image2Rating, $image1Rating);
        $expectedScore2 = getExpectedScore($image1Rating, $image2Rating);
       
        $newRating1 = calculateNewRating($image1Rating, 1, $expectedScore1, $kFactor);
        $newRating2 = calculateNewRating($image2Rating, 0, $expectedScore2, $kFactor);
                    // Update the Elo ratings in the database
        updateImageRating($conn, $image1Id, $newRating1);
        updateImageRating($conn, $image2Id, $newRating2);
}

function second_one($conn, $image1Id,$image2Id) {
              // Get the Elo ratings of the selected images from the database
            $image1Rating = getImageRating($conn, $image1Id);
            $image2Rating = getImageRating($conn, $image2Id);

            $kFactor = 50; // Adjust the k-factor as per your requirement
                      
            $expectedScore1 = getExpectedScore($image2Rating, $image1Rating);
            $expectedScore2 = getExpectedScore($image1Rating, $image2Rating);
          
            $newRating1 = calculateNewRating($image1Rating, 0, $expectedScore1, $kFactor);
            $newRating2 = calculateNewRating($image2Rating, 1, $expectedScore2, $kFactor);
                       // Update the Elo ratings in the database
            updateImageRating($conn, $image1Id, $newRating1);
            updateImageRating($conn, $image2Id, $newRating2);
          }

// Function to retrieve the Elo rating of an image from the database
function getImageRating($conn, $imageId) {
    $query = "SELECT rating FROM images WHERE id = $imageId";
    $result = mysqli_query($conn, $query);
    $row = mysqli_fetch_assoc($result);
    return $row['rating'];
}

// Function to calculate the expected score of an image
function getExpectedScore($ratingA, $ratingB) {
    $expectedScore = 1 / (1 + pow(10, ($ratingB - $ratingA) / 400));
    return $expectedScore;
}

// Function to calculate the new Elo rating of an image
function calculateNewRating($currentRating, $actualScore, $expectedScore, $kFactor) {
    $newRating = $currentRating + $kFactor * ($actualScore - $expectedScore);
    return $newRating;
}

// Function to update the Elo rating of an image in the database
function updateImageRating($conn, $imageId, $newRating) {
    $query = "UPDATE images SET rating = $newRating WHERE id = $imageId";
    mysqli_query($conn, $query);
}

// Close the database connection
mysqli_close($conn);
?>