Hi,
------------ Upgrading Wampserver 2.5 to Wampserver 3.0.3 Directly ------------
Wampserver 2.5 users can apply the update to Wampserver 3.0.3 directly. There will be no change to the Apache, PHP, MySQL settings and versions used; your local sites and databases will not be affected. You will have Wampserver 3.0.3 and all the addons available. In addition this will install Apache 2.4.18, PHP 5.6.18 and 7.0.3, MySQL 5.6.29 and PhpMyAdmin 4.5.4.1. But will not activate them!
You must use first 'Wampserver 2.5 -> 3.0.3 - 32 bit x86' or 'Wampserver 2.5 -> 3.0.3 - 64 bit x64' and NOT 'Wampserver 3.0.6 32/64 bit x86_x64 (Cumulative Update.)'
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Documentation Apache -
Documentation PHP -
Documentation MySQL -
Wampserver install files & addons