php 取服務器文檔根路徑

/**
 * 取服務器文檔根路徑
 * @return string
 */
function getRootPath() {
 $sRealPath = realpath('./');
 $sSelfPath = $_SERVER['PHP_SELF'];
 $sSelfPath = substr( $sSelfPath, 0, strrpos( $sSelfPath, '/' ));
 return substr($sRealPath, 0, strlen($sRealPath) - strlen($sSelfPath));
}