Why </script> does not produce syntax parsing errors in PHP

PHP as a mainstream web building language, in the use of the process there are many traps, the need for programmer ideas.
In the PHP script, if you write the following code
<?php
</script>
?>
This PHP script does not prompt any errors, but directly outputs the "?>". It was incredible, so we wrote the following code
<?php
</div>
?>
This time it prompts parse error, Parse error:syntax error, unexpected ' < ' in ...
Why did the first </script> not prompt the wrong?
Then we need to read the PHP manual again there are various ways of starting a block of PHP code:
You can use four pairs of different start and end tags in PHP. Two of these, <?php?> and <script language= "PHP" > </script> are always available. The other two are short tags and ASP style tags that can be turned on or off in the php.ini configuration file. Although some people find short tags and ASP style tags convenient, they are less portable and generally not recommended.
That is, PHP has 4 tags in it, and <script> is one of them, and like <?php?>, it's always available, and the other two need to be open in the configuration file.
? ... ? > (open via Short_open_tag in configuration file)
<?php ...? >
<script language= "php" > ... </script>
<%%> (ASP style label, discard use in version 5.3.0)
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