可以使用 PHP 的短标签吗？

Question

Here's the information according to the official documentation:

There are four different pairs of opening and closing tags which can be used in PHP. Two of those, <?php ?> and <script language="php"> </script>, are always available. The other two are short tags and ASP style tags, and can be turned on and off from the php.ini configuration file. As such, while some people find short tags and ASP style tags convenient, they are less portable, and generally not recommended.

In my experience most servers do have short tags enabled. Typing

<?=

is far more convenient than typing

<?php echo 

The programmers convenience is an important factor, so why are they not recommended?

转载于:https://stackoverflow.com/questions/200640/are-php-short-tags-acceptable-to-use

Answer 1

They're not recommended because it's a PITA if you ever have to move your code to a server where it's not supported (and you can't enable it). As you say, lots of shared hosts do support shorttags but "lots" isn't all of them. If you want to share your scripts, it's best to use the full syntax.

I agree that <? and <?= are easier on programmers than <?php and <?php echo but it is possible to do a bulk find-and-replace as long as you use the same form each time (and don't chuck in spaces (eg: <? php or <? =)

I don't buy readability as a reason at all. Most serious developers have the option of syntax highlighting available to them.

As ThiefMaster mentions in the comments, as of PHP 5.4, <?= ... ?> tags are supported everywhere, regardless of shorttags settings. This should mean they're safe to use in portable code but that does mean there's then a dependency on PHP 5.4+. If you want to support pre-5.4 and can't guarantee shorttags, you'll still need to use <?php echo ... ?>.

Also, you need to know that ASP tags <% , %> , <%= , and script tag are removed from PHP 7. So if you would like to support long-term portable code and would like switching to the most modern tools consider changing that parts of code.