A brief summary of the difference between single quotes and double quotes in PHP strings. There are double quotes in java strings. There are double quotes in strings. There are double quotes in strings.

Today a friend asked me about the difference, so I can review it by the way.

The difference between single quotes and double quotes:

• " "The fields inside the double quotes will be interpreted by the compiler and then output as HTML code.
• ' 'The words in the single quotes are not interpreted and are output directly.
• The parsing time of single quotes is faster than that of double quotes.
• Single quotes support escape characters, and double quotes support more escape characters.

$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:
Today I saw a foreigner mentioning the issue of single quotes in PHP, and mentioned something interesting. The excerpt is as follows:
It said that after installing the PHP extension Vulcan Logic Disassembler, you can see the PHP-generated Intermediate code,
first is:

echo "This is a string"; 

will be transformed into:

ECHO    'This is a string' 

and

echo 'This is a string'; 

becomes

 ECHO    'This is a string' 

, which is the same
if it is

echo "This is a $variable"; 

PHP The generated OPCODE is

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 

and

echo "This is a " . $variable; 

will become

CONCAT    ~0 'This is a ' !0 

2 ECHO      ~0 

As you can see, the speed is much faster. If you use . to connect

The above has introduced a brief summary of the difference between single quotes and double quotes in PHP strings, including double quotes and string content. I hope it will be helpful to friends who are interested in PHP tutorials.