PHP s database access functions are not standardised. This creates a need for a database class library to hide the differences between the different database API s (encapsulate the differences) so we can easily switch databases. PHP 4.0.5 or later is now required (because we use array-based str_replace).-PHP s database access functions are not standardised. This creates a need for a database class library to hide the differences between the different database API s (encapsulate the differences) so we can easily switch databases. PHP 4.0.5 or later is now required (because we use array-based str_replace).