added database helper including JSON response and input validation utilities

api/db.php

@@ -0,0 +1,90 @@
+<?php
+// =====================================================================
+// Database Helper
+// Provides the PDO Connection and shared Utility Functions for all
+// API Endpoints. Include this File at the Top of every Endpoint.
+// =====================================================================
+
+require_once __DIR__ . '/init.php';
+
+
+// ---------------------------------------------------------------------
+// JSON Response
+// Sends a JSON-encoded Response with the given HTTP Status Code and
+// terminates the Script. Every API Endpoint uses this for Output.
+// ---------------------------------------------------------------------
+function json_response($data, $status_code = 200) {
+    http_response_code($status_code);
+    header('Content-Type: application/json; charset=utf-8');
+    echo json_encode($data, JSON_UNESCAPED_UNICODE);
+    exit;
+}
+
+
+// ---------------------------------------------------------------------
+// Error Response
+// Sends a standardized Error Response with a Message and HTTP Status
+// Code. Uses json_response() internally for consistent Formatting.
+// ---------------------------------------------------------------------
+function error_response($message, $status_code = 400) {
+    json_response(['error' => $message], $status_code);
+}
+
+
+// ---------------------------------------------------------------------
+// Validate Required Fields
+// Checks if all specified Fields exist in the given Data Array and are
+// non-empty. Returns an Array of missing Field Names, or an empty
+// Array if all Fields are present.
+// ---------------------------------------------------------------------
+function validate_required($data, $fields) {
+    $missing = [];
+
+    foreach ($fields as $field) {
+        if (!isset($data[$field]) || trim($data[$field]) === '') {
+            $missing[] = $field;
+        }
+    }
+
+    return $missing;
+}
+
+
+// ---------------------------------------------------------------------
+// Get POST Input
+// Reads and trims all POST Parameters. Returns an associative Array.
+// Falls back to JSON Request Body if no POST Data is present
+// (for Clients that send JSON instead of Form Data).
+// ---------------------------------------------------------------------
+function get_input() {
+    // Check for standard POST Form Data first
+    if (!empty($_POST)) {
+        return array_map('trim', $_POST);
+    }
+
+    // Fall back to JSON Request Body
+    $json = file_get_contents('php://input');
+    $data = json_decode($json, true);
+
+    if (is_array($data)) {
+        return array_map('trim', $data);
+    }
+
+    return [];
+}
+
+
+// ---------------------------------------------------------------------
+// Get PDO Connection
+// Returns the PDO Instance created in init.php. Wrapped in a Function
+// to avoid global Variable Dependencies in Endpoint Files.
+// ---------------------------------------------------------------------
+function get_db() {
+    global $pdo;
+
+    if (!$pdo) {
+        error_response('Database Connection failed.', 500);
+    }
+
+    return $pdo;
+}