PHP magic constants not working

题

When I input this PHP code, the magic constant _LINE_ just gets output literally.

<!DOCTYPE html>
<html>
<body>

<?php

echo "This is line"._LINE_."blah";

?>
</body>
</html>

Output:

 This is line_LINE_

What am I doing wrong?

解决方案

two underscores before and after :

__LINE__

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