Microsoft and open source software maker Zend, whose products create programs that compete with ones built for Windows, said on Tuesday the two companies have struck a long-term partnership.

Bill Hilf, a Microsoft technical strategist, said the Zend deal, a multiyear, multiphase partnership, will ensure that the most popular language computer programmers use to build open source Web applications, PHP, will run on past and future versions of Microsoft Windows Web server software.

This marks a break from the aloofness that has characterized Microsoft’s relations with open source projects. That cool stance forced developers wanting to use PHP software to automatically choose open-source software over Microsoft.

By making PHP applications like SugarCRM, a fast-growing open-source sales and marketing software tool, run as efficiently on Windows-based computers as it does on rival. The pact covers both PHP on the established Windows Server 2003 and the upcoming version, code-named Longhorn.