代码有问题，求解

Question

<?phpecho _FILE_;echo "<br />";echo _LINE_;echo "<br />";echo PHP_VERSION;echo "<br />";echo PHP_OS;echo "<br />";?>

Answer 1

下划线是两个

Answer 2

下划线应该是两个

Answer 3

<?php
echo __FILE__;
echo "<br />";
echo __LINE__;
echo "<br />";
echo PHP_VERSION;
echo "<br />";
echo PHP_OS;
echo "<br />";
?>