php查看当前页面可用变量及常量

function logVars($varList, $excludeList = null) { 
    if ($excludeList == null){
        $excludeList = array('GLOBALS', '_FILES', '_COOKIE', '_POST', '_GET', '_SERVER', '_REQUEST', '_G', 'discuz');  //排除查看的变量名
    }
    $list = array(); 
    foreach ($varList as $key => $value) { 
        if (!in_array($key, $excludeList)){
            $list[$key] = $value; 
        }
    } 
    echo '<pre>'; 
    print_r($list); 
    echo '</pre>'; 
}
logVars(get_defined_vars()); //变量
logVars(get_defined_constants()); //常量