PHP's codice_70 loop was introduced in version 4.0 and made compatible with objects as values in 4.0 Beta 4. However, support for iterators was added in PHP 5 through the introduction of the internal codice_71 interface. The two main interfaces for implementation in PHP scripts that enable objects to be iterated via the codice_70 loop are codice_36 and codice_74. The latter does not require the implementing class to declare all required methods, instead it implements an accessor method (codice_75) that returns an instance of codice_71. The Standard PHP Library provides several classes to work with special iterators. PHP also supports Generators since 5.5.