Improve calling context checks on cli.php (#694)

This commit uses php_sapi_name() against a definite value, rather than
relying on the absense of various superglobals to determine CLI context.

If HTTP is detected, a 404 is issued.

It also adds some additional CLI error outputs, and exit codes for basic
invocation.

Co-authored-by: Rich Lott / Artful Robot <forums@artfulrobot.uk>

cli.php

@@ -14,11 +14,7 @@
 // limitations under the License.
 //
 // $Id$
-// 
-
-require_once('owa_env.php');
-require_once(OWA_DIR.'owa_caller.php');
-require_once(OWA_BASE_CLASS_DIR.'cliController.php');
+//
 
 /**
  * OWA Comand Line Interface (CLI)
@@ -32,28 +28,40 @@
  * @since        owa 1.2.1
  */
 
-define('OWA_CLI', true);
+// Ensure we are being called as a CLI process before any other processing.
+define('OWA_CLI', (php_sapi_name() == 'cli' || (is_numeric($_SERVER['argc']) && $_SERVER['argc'] > 0)));
 
-if (!empty($_POST)) {
-    exit();
-} elseif (!empty($_GET)) {
+if (!OWA_CLI)
+{
+    // Fail with 404 if called over HTTP so it looks like the script
+    // just doesn't exist.
+    if (isset($_SERVER['SERVER_PROTOCOL'])) {
+        header("$_SERVER[SERVER_PROTOCOL] 404 Not Found");
+    }
     exit();
-} elseif (!empty($argv)) {
-    $params = array();
-    // get params from the command line args
-    // $argv is a php super global variable
+}
 
-       for ($i=1; $i<count($argv);$i++)
-       {
-           $it = explode("=",$argv[$i]);
-           $params[$it[0]] = $it[1];
-       }
-     unset($params['action']);
-     unset($params['do']);
+require_once('owa_env.php');
+require_once(OWA_DIR.'owa_caller.php');
+require_once(OWA_BASE_CLASS_DIR.'cliController.php');
 
-} else {
-    // No params found
-    exit();
+$params = [];
+// get params from the command line args
+// $argv is a php super global variable
+for ($i=1; $i<count($argv); $i++)
+{
+    $it = explode("=",$argv[$i]);
+    if (count($it) !== 2) {
+        fwrite(STDERR, "Invalid argument '{$argv[$i]}'. Syntax is key=value\n");
+        exit(1);
+    }
+    $params[$it[0]] = $it[1];
+}
+unset($params['action']);
+unset($params['do']);
+if (empty($params)) {
+    fwrite(STDERR, "Arguments required\n");
+    exit(1);
 }
 
 // Initialize owa
@@ -90,4 +98,4 @@
     $owa->restInPeace();
 }
 
-?>
+?>