added comments to db

api/db.php

@@ -1,8 +1,8 @@
 <?php
 // =====================================================================
 // Database Helper
-// Provides the PDO Connection and shared Utility Functions for all
-// API Endpoints. Include this File at the Top of every Endpoint.
+// Provides PDO Connection to Database and shared miscellaneous
+// Functions for all API Endpoints.
 // =====================================================================
 
 require_once __DIR__ . '/init.php';
@@ -10,12 +10,16 @@ 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.
+// Creates JSON Response including HTTP Status Code and HTTP Header 
+// for every API Endpoint and terminates the Script.
 // ---------------------------------------------------------------------
 function json_response($data, $status_code = 200) {
+    // Defines HTTP Status Code and HTTP Header
+    // 1XX Informational, 2XX Successful, 3XX Redirection,
+    // 4XX Client Error, 5XX Server Error
     http_response_code($status_code);
     header('Content-Type: application/json; charset=utf-8');
+    // Converts PHP-Array to JSON-String
     echo json_encode($data, JSON_UNESCAPED_UNICODE);
     exit;
 }
@@ -23,8 +27,8 @@ function json_response($data, $status_code = 200) {
 
 // ---------------------------------------------------------------------
 // Error Response
-// Sends a standardized Error Response with a Message and HTTP Status
-// Code. Uses json_response() internally for consistent Formatting.
+// Creates standardized Error Responses with Error Message and HTTP Status
+// Code. Uses json_response() for consistent Formatting.
 // ---------------------------------------------------------------------
 function error_response($message, $status_code = 400) {
     json_response(['error' => $message], $status_code);
@@ -33,7 +37,7 @@ function error_response($message, $status_code = 400) {
 
 // ---------------------------------------------------------------------
 // Validate Required Fields
-// Checks if all specified Fields exist in the given Data Array and are
+// Checks if 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.
 // ---------------------------------------------------------------------
@@ -41,28 +45,28 @@ function validate_required($data, $fields) {
     $missing = [];
 
     foreach ($fields as $field) {
+        // Checks if Fields exists in Data Array and are not empty
         if (!isset($data[$field]) || trim($data[$field]) === '') {
             $missing[] = $field;
         }
     }
-
+    // Returns Array of missing Fields or emty Array
     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).
+// Reads POST Parameters. Returns an associative Array.
+// Fallback to JSON Request Body if no POST Data is present.
 // ---------------------------------------------------------------------
 function get_input() {
-    // Check for standard POST Form Data first
+    // Checks for standard POST Requests
     if (!empty($_POST)) {
         return array_map('trim', $_POST);
     }
 
-    // Fall back to JSON Request Body
+    // Fall back for JSON POST Requests
     $json = file_get_contents('php://input');
     $data = json_decode($json, true);
 
@@ -76,8 +80,8 @@ function get_input() {
 
 // ---------------------------------------------------------------------
 // Get PDO Connection
-// Returns the PDO Instance created in init.php. Wrapped in a Function
-// to avoid global Variable Dependencies in Endpoint Files.
+// Returns PDO Instance wrapped in a Function to prevent global 
+// Variable Dependencies in Endpoint Files.
 // ---------------------------------------------------------------------
 function get_db() {
     global $pdo;