Learn PHP from various online tutorial. I recommended that before learn PHP you have good command on HTM and CSS so easily learn PHP try to http://www.w3schools.com/ to learn PHP
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Simple question to answer, but I would rather ask the question of WHY are you asking?
DO you have an issue where someone told you that PHP was the best or only answer? If that is the case, I would like to know what the issue is and then give a relevant answer to that question.