Inconsistent temporary 404s on whole install | PHP error with post-template.php

2 comments

1. There are two types of 404 errors: WordPress-generated, and server-generated.

   In some server environments, 404s could be inaccurately displayed by the server in cases of CPU overload or due to certain instances of misconfiguration, etc. Usually server-generated 404 errors will say something like “Nginx” or “Apache” at the bottom of the page (depends on server type).

   In other situations, “false positive” 404 errors could be generated by WordPress (PHP) because security plugins are blocking access to loaded resources:

   Why am I sometimes getting a 404 error when I try to update a page with Elementor?

   https://wordpress.org/support/topic/getting-false-positive-404-errors-with-newest-update/

   Try disabling any security plugins, clear caches, and refresh the page. Security modules such as ModSecurity installed on your server could also potentially be the cause.

   It could also be caused by a poorly coded theme or plugin. Check if there’s a common theme or plugin installed on all the sites involved. And if this issue only occurs on Media Temple hosting, it’s possible they have something misconfigured, or even that your server is under too much load…

2. You have not enough information to solve your problem. Try to add full stack trace and request information to your error log to investigate an issue.

   You can create your own custom error handler to add stack trace and request information to your error log.

   set_error_handler('wpse_120959_handle_error');
   
   function wpse_120959_handle_error( $errno, $errstr, $errfile, $errline ) {
   
       if( $errno === E_USER_NOTICE ) {
   
           $error = PHP_EOL . PHP_EOL;
   
           $error .= sprintf('You have an error notice: "%s" in file "%s" at line: "%s".', $errstr, $errfile, $errline);
           $error .= wpse_120959_generate_stack_trace() . PHP_EOL;
   
           $error .= 'Request information:' . PHP_EOL;
           $error .= wpse_120959_generate_http_request_info();
   
           error_log( $error );
       }
   }
   
   // Function from php.net http://php.net/manual/en/function.debug-backtrace.php#112238
   function wpse_120959_generate_stack_trace() {
   
       $e = new Exception();
   
       $trace = explode( "n" , $e->getTraceAsString() );
   
       // reverse array to make steps line up chronologically
   
       $trace = array_reverse( $trace );
   
       array_shift( $trace ); // remove {main}
       array_pop( $trace ); // remove call to this method
   
       $length = count( $trace );
       $result = array();
   
       for ($i = 0; $i < $length; $i++) {
           $result[] = ($i + 1)  . ')' . substr( $trace[$i], strpos( $trace[$i], ' ' ) ); // replace '#someNum' with '$i)', set the right ordering
       }
   
       $result = implode("n", $result);
       $result = "n" . $result . "n";
   
       return $result;
   }
   
   function wpse_120959_generate_http_request_info() {
   
       $request_info = '';
       $request_info_format = "%s %s %snHTTP headers:n";
   
       $headers = wpse_120959_get_headers();
       $header_format = "%s: %s n";
   
       $request_method  = filter_input( INPUT_SERVER, 'REQUEST_METHOD', FILTER_SANITIZE_STRING );
       $request_uri     = filter_input( INPUT_SERVER, 'REQUEST_URI', FILTER_SANITIZE_STRING );
       $server_protocol = filter_input( INPUT_SERVER, 'SERVER_PROTOCOL', FILTER_SANITIZE_STRING );
   
       $request_info = sprintf( $request_info_format, $request_method, $request_uri, $server_protocol );
   
       foreach ( $headers as $name => $value ) {
           $request_info .= sprintf( $header_format, $name, $value );
       }
   
       return $request_info;
   }
   
   function wpse_120959_get_headers() {
   
       $headers = [];
   
       foreach ($_SERVER as $name => $value) {
   
           if (preg_match('/^HTTP_/', $name ) ) {
   
               $value = filter_input( INPUT_SERVER, $name, FILTER_SANITIZE_STRING );
   
               $name = strtr( substr( $name, 5 ), '_', ' ');
               $name = ucwords( strtolower( $name ) );
               $name = strtr( $name, ' ', '-' );
   
               // add to list
               $headers[$name] = $value;
           }
       }
   
       return $headers;
   }
   

   You can check if this is working by adding trigger_error somewhere in your code e.g in single.php file.

   trigger_error('Annoying notice');
   

   Your error log should output something like that:

   2018/07/02 14:26:00 [error] 714#714: *58 FastCGI sent in stderr: "PHP message:
   
   You have an error notice: "Annoying notice" in file "/var/www/test/content/themes/twentyseventeen/single.php" at line: "19".
   1) /var/www/test/index.php(17): require('/var/www/test/w...')
   2) /var/www/test/wordpress/wp-blog-header.php(19): require_once('/var/www/test/w...')
   3) /var/www/test/wordpress/wp-includes/template-loader.php(74): include('/var/www/test/c...')
   4) /var/www/test/content/themes/twentyseventeen/single.php(19): trigger_error('Annoying notice')
   5) [internal function]: wpse_120959_handle_error(1024, 'Annoying notice', '/var/www/test/c...', 19, Array)
   
   Request information:
   GET /hello-world/ HTTP/1.1
   HTTP headers:
   Accept-Language: en-US;q=0.8,en;q=0.7
   Accept-Encoding: gzip, deflate
   Referer: http://test.local/
   Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
   User-Agent: Mozilla/5.0 AppleWebKit/604.1.38 (KHTML, like Gecko) Version/11.0 Mobile/15A372 Safari/604.1
   Upgrade-In" while reading upstream, client: 192.168.10.1, server: test.local, request: "GET /hello-world/ HTTP/1.1", upstream: "fastcgi://unix:/var/run/php/php7.2-fpm.sock:", host: "test.local", referrer: "http://test.local"
   

   With this kind of message it will be much easier to find out where the problem is.

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