如果在php字符串的中间使用,'period'字符(。)是什么意思? [英] What does the 'period' character (.) mean if used in the middle of a php string?
问题描述
这是一些示例代码:
p> $ headers ='From:webmaster@example.com'。 \r\\\
。
'回复:webmaster@example.com'。 \r\\\
。
'X-Mailer:PHP /'。 phpversion();
句子字符在每个字符串的中间做什么?
即:
blabla。 blabla。 blablalba;
此运算符用于组合字符串。
EDIT
字符串,它必须转换为一。有关详情,请参见转换为字符串 。
不幸的是,它有时被误用,以至于事情变得更难阅读。这里是好的使用:
echo这是函数的结果:。 myfunction();
这里我们结合一个函数的输出。这是好的,因为我们没有办法使用标准的内联字符串语法。有几种方法不正确地使用此方法:
echo结果是:。 $ result;
这里,你有一个变量 $ result
其中我们可以内联在字符串中:
echo结果是:$ result
另一个难以捕捉误用的方法是:
echo结果是:。 $ myarray ['myvalue']。 和。 $ class-> property;
如果你不知道 {}
内联变量的转义序列:
echo结果是:{$ myarray ['myvalue' ]}和{$ class-> property};
关于引用的例子:
$ headers ='From:webmaster@example.com'。 \r\\\
。
'回复:webmaster@example.com'。 \r\\\
。
'X-Mailer:PHP /'。 phpversion();
这有点麻烦,因为如果我们不使用连接运算符,换行符,因此这会强制换行以\r\\\
结尾。我认为这是一个更不寻常的情况,由于电子邮件头的限制。
请记住,这些连接运算符打破字符串,使事情有点难以阅读,只有在必要时才使用它们。
I'm fairly new to PHP, but I can't seem to find the solution to this question in google.
Here is some example code:
$headers = 'From: webmaster@example.com' . "\r\n" .
'Reply-To: webmaster@example.com' . "\r\n" .
'X-Mailer: PHP/' . phpversion();
what does the period character do in the middle of each piece of the string?
ie: "blabla" . "blabla" . "blablalba";
This operator is used to combine strings.
EDIT
Well, to be more specific if a value is not a string, it has to be converted to one. See Converting to a string for a bit more detail.
Unfortunately it's sometimes mis-used to the point that things become harder to read. Here are okay uses:
echo "This is the result of the function: " . myfunction();
Here we're combining the output of a function. This is okay because we don't have a way to do this using the standard inline string syntax. A few ways to improperly use this:
echo "The result is: " . $result;
Here, you have a variable called $result
which we can inline in the string instead:
echo "The result is: $result";
Another hard to catch mis-use is this:
echo "The results are: " . $myarray['myvalue'] . " and " . $class->property;
This is a bit tricky if you don't know about the {}
escape sequence for inlining variables:
echo "The results are: {$myarray['myvalue']} and {$class->property}";
About the example cited:
$headers = 'From: webmaster@example.com' . "\r\n" .
'Reply-To: webmaster@example.com' . "\r\n" .
'X-Mailer: PHP/' . phpversion();
This is a bit tricker, because if we don't use the concatenation operator, we might send out a newline by accident, so this forces lines to end in "\r\n" instead. I would consider this a more unusual case due to restrictions of email headers.
Remember, these concatenation operators break out of the string, making things a bit harder to read, so only use them when necessary.
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