Propagate failure in HTML generation

php/generate-html.php

@@ -30,15 +30,22 @@
 			$relpath = str_replace($TEMPLATES_ROOT, "", $phppath);
 			$docpath = str_replace(".php", ".html", $docpath);
 
-			// This works? Yes, yes it does.
 			// We do this to isolate the environment and include-once triggers,
 			// otherwise we could include the documents in an ob_* wrapper.
 
-			// Same as shell_exec, except we don't have to escape quotes.
 			log_info("Generating output for $relpath.");
-			$document = `cd "$TEMPLATES_ROOT"; php $phppath $flags`;
+			$output = [];
 
-			file_put_contents($docpath, $document);
+			$exit_code = 0;
+
+			exec("cd '$TEMPLATES_ROOT'; php '$phppath' $flags", $output, $exit_code);
+
+			if ($exit_code != 0 || empty($output)) {
+				log_error("HTML generation failed.");
+				exit(255);
+			}
+
+			file_put_contents($docpath, join("\n", $output));
 		}
 
 		log_info("Done generating HTML.");