In the PHP regular expression. *? What does that mean?

Non-greedy mode
. * Will match all subsequent characters, that is, to the end of the meaning
Add? After that is not greedy mode, this time to see? What's the character behind it, like. *? " It means that the match ends when you encounter double quotes.

.*?> means to meet > match end

For example:

5. Write a regular expression that js/vbs all the scripts on the Web page (that is, remove the script tag and its contents):
 
<?php $script = "The following does not appear:
<script language= ' javascript ' >alert (' cc ');</script> "; Echo
Preg_replace ("/<script[^>].*?>.*?</script>/si", "Replacement content", $script);?>

In the PHP regular expression. *? What does that mean?