You need to have the php_mbstring module enabled in your php.ini. Some setups have it disabled by default.

If that's not possible, you can try changing mb_strlen() to just strlen() in the file referenced in the error message.

PHP 5.3 requires a timezone setting. There are several possible fixes (use the appropriate timezone for your location). The list of possible settings is here.

Put something like this in your php.ini file:

date.timezone = "America/Chicago"

If you don't have access to php.ini, you can try adding this to your .htaccess file:

php_value date.timezone America/Chicago

If you don't have access to the php.ini file and modifying .htacces gives you an error, you can try putting this line in the index.php file in the MODX site root:

date_default_timezone_set('America/Chicago');

If none of these work, you'll need to contact your hosting service.

Note: If you're using XAMPP, you can modify /xampp/apache/bin/php.ini.

This is a fairly generic error so there's no one thing that causes it.

One common possibility is file permissions. If your host uses suExec or suPHP, the permissions on folders should be 755 and files should be set to 644. Usually this is done by going to cPanel (or the equivalent) at your host and clicking on "File Manager." In File Manager, you navigate to the file or directory you want to change (your site will normally be under public_html). You'll see the permission numbers on the right as you go. When you get to the target file or directory, click on its name, then on "change permissions." An even easier method, if it works on your host, is to use the free FileZilla FTP program which allows you to set permissions for all files and folders recursively.

Another, less common, possibility is a bug in the MODx SearchHighlighting Plugin. Disabling the plugin will solve the problem.

On some hosts, having a php directive in the .htaccess file will generate a Server 500 error.
Example:

php_flag zlib.output_compression On

The solution is to comment out the php_flag lines with a '#' character at the beginning:

#php_flag zlib.output_compression On

Having an unpublished error document on the MODx site can also cause a 500 error under some circumstances.

Another possiblity is having a "rewrite engine on" statement in an .htaccess file and another .htaccess file in a directory below that one that also contains the same line.

If you get a 500 error when you turn on Friendly URLs with XAMPP on localhost, make sure you have these in your xampp/apache/conf/httpd.conf (without the # comment token at the beginning):

LoadModule rewrite_module modules/mod_rewrite.so
AllowOverride All

If you are getting this error on a site you moved by exporting and importing the SQL, be sure you have enabled DROP TABLE and CREATE TABLE in the export.

There are three deprecated system settings that need to be deleted from the modx_system_settings table in the database: session_name, session_cookie_path, and session_cookie_domain. Once you've removed them in PhpMyAdmin, delete the core/cache/config.cache.php file, clear your browser cache and cookies, and login again.

MODx tries to increase the memory limit if you are short, but it doesn't always work. Being short of memory should generate an error during install, but sometimes the install will appear to complete normally even though there wasn't enough memory to do the job right. This can result in all kinds of weird errors when you try to use MODx. The solution is to increase your memory_limit and rerun the install.

Increasing the amount of memory depends on your host. You may be able to add this php directive in your .htaccess file:

php_value memory_limit 128M

If that doesn't work, you may be able to edit or add a php.ini file and change the memory limit:

memory_limit = 128M

Note that the server has to be restarted for the changes in memory_limit to take effect. In some cases, you'll have to ask your hosting service to increase your memory limit (or change hosts).

If I had a dime for every user who said that but had mistyped or misremembered one or the other . . . That said, it could mean that MODx ran out of memory during the install. See "out of memory" above. Also, see the thread here.

• Be sure to use "localhost" as the database server name. It's almost always correct.
• If MODx has trouble creating the database, you may have to do it yourself. Make sure to create a user and give the user full rights to the database. That user's username and password are what you need for the database connection form during the MODx install — not your MODx username and password.
• Some hosts add a prefix to the database name and/or database username so the names you entered when you created the DB/User may not be the real ones.
• The next best guess here is either a too-old version of PHP, a PHP/MySQL version mismatch, or a misconfigured or disabled PHP or MySQL install.
• Also possible are a non-standard port, or a name other than "localhost" for the database server.

MODx uses an index.php file in the root of the site to dispatch the user to its various pages. You probably still have an index.html or index.htm page in the site root. You need to rename it or tell Apache to give index.php priority as the index page. Look here or add this code to the .htaccess file in the MODx root directory:

DirectoryIndex index.php

Unlike MODx Evolution, Revolution is installed with no content. You need to create a document resource and make it the home page.

Unlike MODx Evolution, Revolution is installed with no snippets or plugins. You need go to System | Package Management and click on "Download Extras." Then download TinyMCE and any other add-on componenents you need for your site. Then install them by right clicking on them and selecting "Install."

Unlike MODx Evolution, Revolution is installed with no snippets or plugins. You need go to System | Package Management and click on "Download Extras." Then download TinyMCE and any other add-on componenents you need for your site. Then install them by right clicking on them and selecting "Install."

Yes. That spot is available for third-party components that want to add custom Manager pages. You install the components in System | Package Management.

If you have moved your site, be sure to do an Upgrade Install at the new site. Try clearing your browser cache and cookies and, if you can access the MODx Manager, clear the MODx cache as well. If you can't access the Manager, go to the core/cache directory and delete everything in it but index.php.

Sometimes, one or more MODx files is corrupted in download or upload. MODx has a lot of files and this happens more often than you might think. If everything else fails, try downloading and installing again.

This is often a mod_security problem that has to do with how MODx objects are saved to the database. Look here for more information on making the problem go away.

This is often caused by having PHP's safe_mode on. See this link for more information.

This is another problem that has multiple causes. Here are some possibilities:

• Installing MODx Revolution over an earlier version
• core/cache directory is not writable
• Permission issue with MODx directories and files
• Not enough memory for proper install (see "out of memory" above)
• Very old version of MySQL or PHP

Things to try:

1. Make sure your memory_limit is at least 64M
2. Make sure the following directories are writable:
   • / (MODx root directory)
   • /core/packages
   • core/cache
   • core/export
   • /manager
   • /connectors
3. Create an empty file: "/core/config/config.inc.php" and make it writable.
4. Use the "Regular" version of Revolution instead of the "Advanced" version.

The FAQ uses some JavaScript code from DynamicDrive.com and is extremely easy to create and maintain in MODx thanks to the EZfaq Snippet, created by (ahem) me. Go here to see the EZfaq tutorial.