PHP is very famous languages with very good demand in the market. At the right time there is supply less of PHP coders in the market which makes it difficult to command a premium pricing in the market. A skilled PHP developer should have basic knowledge of other scripting language such as HTML, Javascript, Jquary, CSS, CSS3, Sql, They must have in depth knowledge of one on one PHP frameworks like Joomla, Drupal, Cakephp, Zend, Laravel codelgniter etc. They are also responsible for developing and integrating various plugins.