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
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.
I'm too fond of <?=$whatever?> to let it go. Never had a problem with it. I'll wait until it bites me in the ass. In all seriousness, 85% of (my) clients have access to php.ini in the rare occasion they are turned off. The other 15% use mainstream hosting providers, and virtually all of them have them enabled. I love 'em.
Short tags are coming back thanks to Zend Framework pushing the "PHP as a template language" in their default MVC configuration. I don't see what the debate is about, most of the software you will produce during your lifetime will operate on a server you or your company will control. As long as you keep yourself consistent, there shouldn't be any problems.
UPDATE
After doing quite a bit of work with Magento, which uses long form. As a result, I've switched to the long form of:
<?php and <?php echo
over
<? and <?=
Seems like a small amount of work to assure interoperability.
The problem with this whole discussion lies in the use of PHP as a templating language. No one is arguing that tags should be used in application source files.
However PHP's embeddable syntax allows it to be used as a powerful template language, and templates should be as simple and readable as possible. Many have found it easier to use a much slower, add-on templating engine like Smarty, but for those purists among us who demand fast rendering and a pure code base, PHP is the only way to write templates.
The ONLY valid argument AGAINST the use of short tags is that they aren't supported on all servers. Comments about conflicts with XML documents are ludicrous, because you probably shouldn't be mixing PHP and XML anyway; and if you are, you should be using PHP to output strings of text. Security should never be an issue, because if you're putting sensitive information like database access credentials inside of template files, well then, you've got bigger issues!
Now then, as to the issue of server support, admittedly one has to be aware of their target platform. If shared hosting is a likely target, then short tags should be avoided. But for many professional developers (such as myself), the client acknowledges (and indeed, depends on the fact) that we will be dictating the server requirements. Often I'm responsible for setting up the server myself.
And we NEVER work with a hosting provider that does not give us absolute control of the server configuration -- in such a case we could count on running to much more trouble than just losing short tag support. It just doesn't happen.
So yes -- I agree that the use of short tags should be carefully weighed. But I also firmly believe that it should ALWAYS be an option, and that a developer who is aware of his environment should feel free to use them.
Starting with PHP 5.4, the echo shortcut is a separate issue from short tags, as the echo shortcut will always be enabled. It's a fact now:
So the echo shortcut itself (<?=) is safe to use now.