在PHP中创建字符串时“和”之间有什么区别？

Very basic, but would like to know the difference/security ramifications etc of using " vs. '.

非常基本,但想知道使用“vs.”的差异/安全后果等。

Can someone provide an example that explains when to use each one?

有人可以提供一个解释何时使用每个人的例子吗?

3 个解决方案

#1

There are a lot of subtle differences, you'll want to read the php documentation to get a lot of the details, but the important detail are:

有很多细微的差别,你需要阅读php文档来获取很多细节,但重要的细节是:

Double quotes are parsed whereas single quotes are literals.

解析双引号,而单引号是文字。

You can use variables inline with double quotes, but not with single quotes.

您可以使用带双引号的内联变量,但不能使用单引号。

There are some catches though:

虽然有一些捕获:

<?php
$beer = 'Heineken';
echo "$beer's taste is great"; // works; "'" is an invalid character for variable names
echo "He drank some $beers";   // won't work; 's' is a valid character for variable names but the variable is "$beer"
echo "He drank some ${beer}s"; // works
echo "He drank some {$beer}s"; // works
?>

Single quotes are slightly faster.

单引号稍快一些。

#2

When a string is enclosed in double quotes, then escape sequences such as \n and variable identifiers such as $var are interpreted.

当字符串用双引号括起来时,将解释转义序列(如\ n)和变量标识符(如$ var)。

See the PHP strings manual for specific details and examples.

有关具体细节和示例,请参阅PHP字符串手册。

#3

The biggest one is this. Inside double-quotes, you can include variables, but inside single quotes, the variable name will be literal:

最大的就是这个。在双引号内,您可以包含变量,但在单引号内,变量名称将是文字:

$var1 = "hello";

// this will echo "hello world"
echo "$var1 world";

// this will echo $var1 world
echo '$var1 world';

Using double-quotes becomes extremely useful in a number of situations, expecially when you place {} around the variable names. Here are some examples (certainly others can give you more examples):

在许多情况下使用双引号变得非常有用,特别是当您在变量名称周围放置{}时。以下是一些示例(当然其他人可以提供更多示例):

// array elements
echo "Element 5 is {$myArray[5]}";
echo "Element 2 subelement 3 is {$myArray[2][3]}";
//
// a dynamic key 
$value = "thing";
$someValue = $myArray["some{$value}"]; // returnd $myArray[something]

#1