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<?php /** * Demonstration of a PHP bug: Capturing output as a string with an output buffer stops working * as soon as PHP has detected a client disconnect. * * Verified with different PHP 5.4 and 5.5 builds on Linux and Win7 with Apache 2.2, Apache 2.4 * and PHP-FPM SAPIs. * * PHP-FPM note: When testing with PHP-FPM, make sure the web server does not buffer the reponse. * For nginx, set "gzip off;" and "fastcgi_buffering off;" (only supported by version 1.6 and * above) in the vhost configuration. */ // We record the results in this file after the client connection was closed define('LOG_FILE', __DIR__ . '/ob-bug-test' . PHP_VERSION . '.log'); ini_set('error_log', __DIR__ . '/error.log'); // Let's not bother with HTML... header('Content-Type: text/plain; charset=utf-8'); // Prevent script from exiting when client disconnects ignore_user_abort(true); // Flush & close all output buffers to make the echo/flush calls // below send data to the client immediately while (ob_get_level()) { ob_end_flush(); } // Init log file echo "Results will go to " . LOG_FILE . "\n"; log_message("\n" . date('# Y-m-d H:i:s')); // Run the tests once before the client disconnects test_echo_output_buffer_capturing(); test_gd_output_buffer_capturing(); // Wait until client has closed connection while (!connection_aborted()) { log_message("\nClient is still connected"); // PHP only detects a client disconnect when trying to actually // send rsponse data to the client echo "Abort the request in your browser now by pressing " . "<Esc> or clicking the little X in the adress bar...\n"; flush(); sleep(1); } log_message("\nClient is now disconnected (connection_aborted() returns true)"); // Run the tests again, after client has disconnected test_echo_output_buffer_capturing(); test_gd_output_buffer_capturing(); // ============================================================================= /** * This is what e.g. the popular template engine Twig does when rendering a template. * * A common case when this might happen after client diconnect: when Twig is used to * render the body of an e-mail at the end of a long-running request. */ function test_echo_output_buffer_capturing() { ob_start(); echo 'Hello World'; $captured_output = ob_get_clean(); log_message("\nCapture echo in output buffer:"); log_message(' - captured string length: ' . strlen($captured_output)); } /** * The GD image output functions can either write to a file or to stdout. * * When the binary image data is needed as a string to e.g. write it to a DB blob field, * using an output buffer is a shorter and faster method than writing to a temp file. */ function test_gd_output_buffer_capturing() { // $img = imagecreatetruecolor(100, 100); // ob_start(); // // second imagejpeg() arg === null means "send image data to client/stdout" // // Really strange behaviour: when the client connection is closed, imagejpeg() // // triggers a warning (unrecoverable error) but returns true!? // $success = imagejpeg($img, null, 100); // $captured_output = ob_get_clean(); // imagedestroy($img); // log_message("\nCapture binary image data in output buffer:"); // log_message(' - image data length: ' . strlen($captured_output)); // log_message(' - imagejpeg() return value: ' . ($success ? 'true' : 'false')); } function log_message( $message ) { if (false === file_put_contents(LOG_FILE, $message . "\n", FILE_APPEND)) { die("Sorry, it seems " . LOG_FILE . " is not writable. Aborting...\n"); } }

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