简单概括PHP的字符串中单引号与双引号的区别，php字符串-php手册-php.cn

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简单概括PHP的字符串中单引号与双引号的区别，php字符串

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Jun 13, 2016 am 08:41 AM

phpapostropheDouble quotes

简单概括PHP的字符串中单引号与双引号的区别，php字符串

今天有个朋友问起,说下区别,顺便复习下。

单引号与双引号的不同：

" "双引号里面的字段会经过编译器解释，然后再当作HTML代码输出。
' '单引号里面的不进行解释，直接输出。
单引号解析的时间比双引号快。
单引号支持\转义符,双引号支持的转义符更多。

$hello= 3;
echo "hello is $hello"; // 打印结果:hello is 3 
echo 'hello is $hello'; // 打印结果: hello is $hello 
echo "hello is $hello\n"; // 打印结果: hello is 2 (同时换行) 
echo 'hello is $hello\n'; // 打印结果: hello is $hello\n

PS：
今天看到老外提到了PHP的单引号的问题，其中提到了有趣的东西，摘录如下：
其中说装了PHP扩展 Vulcan Logic Disassembler 后，可以看到PHP生成的中间码，
首先是：

echo "This is a string";

会转变为：

ECHO    'This is a string'

而

echo 'This is a string';

则变成

 ECHO    'This is a string'

，是一样的
如果是

echo "This is a $variable";

则PHP产生的OPCODE为

INIT STRING ~0 

2 ADD_STRING  ~0 ~0 'This' 

3 ADD_STRING  ~0 ~0 ' ' 

4 ADD_STRING  ~0 ~0 'is' 

5 ADD_STRING  ~0 ~0 ' ' 

6 ADD_STRING  ~0 ~0 'a' 

7 ADD_STRING  ~0 ~0 ' ' 

8 ADD_VAR    ~0 ~0 !0 

9 ECHO      ~0

而

echo "This is a " . $variable;

则会变成

CONCAT    ~0 'This is a ' !0 

2 ECHO      ~0

可以见到，速度快很多了，用.连接的话

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