<?php

/**

* Gracefully handles runtime environment fallback and diagnostics with error logging.

*/

// Define fallback environment variables and their defaults.

$fallback_env = [

'DEBUG' => false,

'LOG_DIR' => 'logs',

'ENVIRONMENT' => 'fallback',

];

// Merge environment variables with defaults.

$_ENV = array_merge($_ENV, $fallback_env);

// Error logging function.

function logError($message) {

global $LOG_DIR;

$timestamp = date('Y-m-d H:i:s');

$logFile = $LOG_DIR . '/' . $timestamp . '.log';

error_log("[$timestamp] ERROR: $message", 3, $logFile); // Log to file

error_log("[$timestamp] ERROR: $message", 3, null); //Also send to standard error stream

}

// Check for environment variables.

if (!isset($_ENV['DEBUG'])) {

$_ENV['DEBUG'] = false; //Default to false if not set

}

if (!isset($_ENV['LOG_DIR'])) {

$_ENV['LOG_DIR'] = 'logs'; //Default log directory

}

if (!isset($_ENV['ENVIRONMENT'])) {

$_ENV['ENVIRONMENT'] = 'fallback'; //Default environment

}

// Diagnostic logging

if ($_ENV['DEBUG']) {

// Log basic environment information.

logError("--- Environment Diagnostics ---");

logError("DEBUG: Environment: " . $_ENV['ENVIRONMENT']);

logError("DEBUG: Debug Mode: " . $_ENV['DEBUG']);

logError("DEBUG: Log Directory: " . $_ENV['LOG_DIR']);

logError("DEBUG: PHP Version: " . phpversion());

logError("DEBUG: Server OS: " . PHP_OS);

logError("DEBUG: Server Architecture: " . PHP_SAPI);

//Example of checking if a specific function exists

if(function_exists('mysqli_connect')){

logError("DEBUG: mysqli_connect function available.");

} else {

logError("DEBUG: mysqli_connect function NOT available.");

}

}

//Example usage: Implement your application logic here.

//If certain features require a specific environment, you can check $_ENV['ENVIRONMENT'] and handle accordingly.

?>