In PHP, why does not show a parse error?

This must be because there are various ways of starting a block of PHP code:

• <? ... ?> (known as short_open_tag)

• <?php ... ?> (the standard really)

• <script language="php"> ... </script> (not recommended)

• <% ... %> (deprecated and removed ASP-style tag after 5.3.0)

Apparently, you can open a PHP block one way, and close it the other. Didn’t know that.

So in your code, you opened the block using <? but PHP recognizes </script> as the closer. What happened was:

<?php       <----- START PHP
</script>   <----- END PHP
?>          <----- JUST GARBAGE IN THE HTML