php echo无法打印

I am new to PHP. I am developing php under Redhat.

The index.html is like this:

<?php
    $myvar="AAAA";
    echo $myvar;
?>

But nothing is output in the browser.

Any help?

Rename the file to index.php and it should work.

If that fixes it the problem was that the webserver (presumably Apache) knows that .php files should be rendered with PHP but it correctly ignores .html files.

From what i see, the file is interpreted as HTML and not PHP. If you see the source of the page, you will see your PHP code. Try renaming the file to index.php and if your server is set up properly, it should interpret the PHP code.

Change the file extension from .html to .php and your code will work fine.