<documentation title="Including Code"> <standard> <![CDATA[ Anywhere you are unconditionally including a class file, use <em>require_once</em>. Anywhere you are conditionally including a class file (for example, factory methods), use <em>include_once</em>. Either of these will ensure that class files are included only once. They share the same file list, so you don't need to worry about mixing them - a file included with <em>require_once</em> will not be included again by <em>include_once</em>. ]]> </standard> <standard> <![CDATA[ Note that <em>include_once</em> and <em>require_once</em> are statements, not functions. Parentheses should not surround the subject filename. ]]> </standard> <code_comparison> <code title="Valid: used as statement"> <![CDATA[ require_once 'PHP/CodeSniffer.php'; ]]> </code> <code title="Invalid: used as function"> <![CDATA[ require_once<em>(</em>'PHP/CodeSniffer.php'<em>)</em>; ]]> </code> </code_comparison> </documentation>