PHP 标记

当解析一个文件时,PHP 会寻找起始和结束标记,也就是 <?php?>,这告诉 PHP 开始和停止解析二者之间的代码。此种解析方式使得 PHP 可以被嵌入到各种不同的文档中去,而任何起始和结束标记之外的部分都会被 PHP 解析器忽略。

PHP 也允许使用短标记 <??>,但不鼓励使用。只有通过激活 php.ini 中的 short_open_tag 配置指令或者在编译 PHP 时使用了配置选项 --enable-short-tags 时才能使用短标记。

如果文件内容是纯 PHP 代码,最好在文件末尾删除 PHP 结束标记。这可以避免在 PHP 结束标记之后万一意外加入了空格或者换行符,会导致 PHP 开始输出这些空白,而脚本中此时并无输出的意图。

<?php
echo "Hello world";

// ... more code

echo "Last statement";

// 脚本至此结束,并无 PHP 结束标记

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User Contributed Notes 4 notes

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-4
mario
18 days ago
A few related notes, partly covered elsewhere in the manual:

  → Since PHP 5.4 the inline echo <?= ?> short tags are always
    enabled regardless of the short_open_tag (php.ini) setting.

  → PHP tags are infrequently also referred to as open/close "tokens"
    (as per the tokenizers T_OPEN_TAG / _ECHO, and T_CLOSE_TAG naming).

  → The historic ASP-style <% %> and even more rarely used
    <script language=PHP></script> tags are to be repealed in PHP7.
    http://wiki.php.net/rfc/remove_alternative_php_tags

There also exists a small tool called "phptags tidier" for consistently rewriting PHP short/long tags.  It's suitable to normalize include and template scripts, e.g. employ the always-enabled long <?php ?> tags, and/or relieve whitespace padding before/after PHP tags:

    phptags --long --whitespace --warn  *.php

Instead of reliably fixing the common whitespace/BOM issues around tags, it can also just remove all ?> close tags with `--unclose --tokenizer` as advised afore.
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-22
alexander dot podgorny at somewhere dot com
1 month ago
One reason to use long tags over short is to avoid confusion with <?xml ?> notation.
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-25
billscloud dot mail at gmail dot com
1 month ago
In your paragraph you need to close your bracket.

<grammernazi>Me</grammarnazi>
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-65
preda dot vlad at yahoo dot com
1 year ago
So here are the valid ways to open PHP tags:

<?php ?> // standard tags
<? ?> // short tags, need short_open_tag enabled in php.ini
<% %> // asp tags, need asp_tags enabled in php.ini
<script language="php"> </script> // case insensitive

PSR-1 coding standards suggest to only use <?php ?> or <?= ?> (echo short tags) - and no other variations, and PSR-2 suggests to not close the tags in PHP only files.
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