ob_get_contents 获取输出缓存内容

function _require($filename)
{
    ob_start();
    include $filename;
    $content = ob_get_contents();
    ob_end_clean();

    return $content;
}
include 引入的内容也可以在输入缓存中获取

if (!function_exists('version_compare') || version_compare(phpversion(), '5.3.0', '<')) {
    return preg_replace("/{([^}{
]*)}/e", "$this->select('\1');", $source);
} 

php 版本比较函数