There's a spell checking module available for PHP called pspell but if it's not already installed on your server it needs downloading, installing and configuring before you can use it. But if you want to ensure your code will work on any server, this plug-in provides a reasonably fast spell checker based on a dictionary of over 80,000 words along with the plug-ins.

The Figure shows a paragraph from Dickens' A Tale of Two Cities, but this time some deliberate spelling errors have been introduced, which have been caught by the plug-in.

Checking user input for spell checking is easily accomplished with this plug-in