View file zip0.ru/friends_action.php

<?php
require_once 'db.php';

if (empty($_SESSION['user_id'])) {
    header('Location: login.php');
    exit;
}

$current_id = (int)$_SESSION['user_id'];
$action     = $_POST['action'] ?? '';
$target_id  = isset($_POST['target_id']) ? (int)$_POST['target_id'] : 0;

if ($target_id <= 0 || $target_id === $current_id) {
    header('Location: browse.php');
    exit;
}

function redirect_back($target_id) {
    header('Location: user.php?user_id=' . $target_id);
    exit;
}

if ($action === 'add') {
    // проверяем, нет ли уже записи
    $stmt = $mysqli->prepare("
        SELECT id, requester_id, addressee_id, status
        FROM friendships
        WHERE (requester_id = ? AND addressee_id = ?)
           OR (requester_id = ? AND addressee_id = ?)
        LIMIT 1
    ");
    $stmt->bind_param('iiii', $current_id, $target_id, $target_id, $current_id);
    $stmt->execute();
    $rel = $stmt->get_result()->fetch_assoc();
    $stmt->close();

    if ($rel) {
        // если раньше было declined – переотправляем
        if ($rel['status'] === 'declined') {
            $stmt = $mysqli->prepare("
                UPDATE friendships
                SET requester_id = ?, addressee_id = ?, status = 'pending', requester_notified = 0, created_at = NOW()
                WHERE id = ?
            ");
            $stmt->bind_param('iii', $current_id, $target_id, $rel['id']);
            $stmt->execute();
            $stmt->close();
        }
    } else {
        $stmt = $mysqli->prepare("
            INSERT INTO friendships (requester_id, addressee_id, status, requester_notified)
            VALUES (?, ?, 'pending', 0)
        ");
        $stmt->bind_param('ii', $current_id, $target_id);
        $stmt->execute();
        $stmt->close();
    }
    redirect_back($target_id);
}

if ($action === 'accept') {
    // принимаем заявку и оставляем requester_notified = 0,
    // чтобы отправителю показалось уведомление
    $stmt = $mysqli->prepare("
        UPDATE friendships
        SET status = 'accepted', requester_notified = 0
        WHERE requester_id = ? AND addressee_id = ? AND status = 'pending'
    ");
    $stmt->bind_param('ii', $target_id, $current_id);
    $stmt->execute();
    $stmt->close();
    redirect_back($target_id);
}

if ($action === 'decline') {
    $stmt = $mysqli->prepare("
        UPDATE friendships
        SET status = 'declined', requester_notified = 0
        WHERE requester_id = ? AND addressee_id = ? AND status = 'pending'
    ");
    $stmt->bind_param('ii', $target_id, $current_id);
    $stmt->execute();
    $stmt->close();
    redirect_back($target_id);
}

if ($action === 'remove') {
    $stmt = $mysqli->prepare("
        DELETE FROM friendships
        WHERE status = 'accepted'
          AND (
              (requester_id = ? AND addressee_id = ?)
           OR (requester_id = ? AND addressee_id = ?)
          )
    ");
    $stmt->bind_param('iiii', $current_id, $target_id, $target_id, $current_id);
    $stmt->execute();
    $stmt->close();
    redirect_back($target_id);
}

// по умолчанию просто назад на профиль
redirect_back($target_id);