The following functions work on dBase files, which typically end with a .dbf extension. If you are using the precompiled version for Windows, you will need to load the dBase extension by editing php.ini or using the dl function. The extension is likely called php_dbase.dll but was unavailable at the time of this writing. On other operating systems it's easy to compile dBase support into PHP.
The dBase functionality in PHP is somewhat limited. Index and memo fields are not supported. Neither is any kind of locking. The dBase functionality in PHP is meant to be a means of importing data from what has become somewhat of a lowest common denominator in data exchange.
Jim Winstead added dBase support to PHP.