LaravelConf Taiwan 2019 announcement

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

up
0
kuzawinski dot marcin at gmail dot com
4 days ago
New lines placed after PHP closing tags are ignored;

<?= "A"?>
B
<?= "C"?>

Output:
AB
C
up
1
crazytonyi at gmail dot com
3 years ago
Regarding earlier note by @purkrt :

> I would like to stress out that the opening tag is "<?php[whitespace]", not just "<?php"

This is absolutely correct, but the wording may confuse some developers less familiar with the extent of the term "[whitespace]".

Whitespace, in this context, would be any character that generated vertical or horizontal space, including tabs ( \t ), newlines ( \n ), and carriage returns ( \r ), as well as a space character ( \s ). So reusing purkrt's example:

<?php/*blah*/ echo "a"?>

would not work, as mentioned, but :

<?php /*php followed by space*/ echo "a"?>

will work, as well as :

<?php
/*php followed by end-of-line*/ echo "a"?>

and :

<?php    /*php followed by tab*/ echo "a"?>

I just wanted to clarify this to prevent anyone from misreading purkrt's note to mean that a the opening tag --even when being on its own line--required a space ( \s ) character. The following would work but is not at all necessary or how the earlier comment should be interpreted :

<?php
/*php followed by a space and end-of-line*/ echo "a"?>

The end-of-line character is whitespace, so it is all that you would need.
up
-11
Mark Clements (kennel17.co.uk)
1 year ago
Closing PHP tags are recognised within single-line comments:

    <?php
   
// Code will end here ?> This is output as literal text.

    <?php
   
# Same with this method of commenting ?> This is output as literal text.

However they do not have an effect in C-style comments:

    <?php
   
/* Code will not end here ?> as closing tags are ignored inside C-style comments. */
   
?>
up
-22
pl at dot pl
3 months ago
Omit closing tag ?> always whenever you can

example:
<!DOCTYPE html><head>
<title><?php include'varia.php'; echo$title?></title>
</head><body></body></html>

varia.php
<?php
$title
= 'Welcome';
?>
[new line]        //other words: an extra 'Enter' is guilty
---------------

and you get:

Welcome - at the browser label

source won't tell you what happened - there will be fine:

<!DOCTYPE html><head>
<title>Welcome</title>
</head><body></body></html>

Now imagine, what else can go wrong because of it? Everything, as Murphy said.
And you will look for the answer why...? And where...?
It's just simplest example.
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