linux环境安装了lua，但是php中class_exists判断为false，请问我该如何排查？

<code>出错的代码如下，class_exists("Lua",false)为false，我在linux下输入lua，能够调用lua，请问我该如何进一步排查：public function getTableData($tableName) {    $gameTable = array();    if (class_exists("Lua",false)) {        $lua = new Lua ();        $lua->eval ( </code>

<code>        $tablePath = GAME_LUA_PATH . "clientData/?.lua;";        $tablePath .= GAME_LUA_PATH . "serverData/?.lua;";        $gameTable = $lua->getTable ( $tablePath, $tableName );    }else {        exit("lua has not been installed");    }    return $gameTable;}</code>