A brief summary of the difference between single quotes and double quotes in a PHP string.

A brief summary of the difference between single quotes and double quotes in a PHP string.

Today, a friend asked me about the difference. Let's review it by the way.

Single quotes and double quotes are different:

• "" Fields in double quotation marks are interpreted by the compiler and then output as HTML code.
• ''Is output directly without being interpreted in single quotes.
• The time for parsing single quotes is faster than that of double quotes.
• Single quotation marks support \ escape characters, and double quotation marks support more escape characters.

$ Hello = 3; echo "hello is $ hello"; // print the result: hello is 3 echo 'Hello is $ hello'; // print the result: hello is $ hello echo "hello is $ hello \ n"; // print the result: hello is 2 (line feed) echo 'Hello is $ hello \ n '; // print the result: hello is $ hello \ n

PS:
Today, I saw foreigners mention the single quotes of PHP, and some interesting things are mentioned. The excerpt is as follows:
After installing the PHP extension Vulcan Logic discycler, you can see the intermediate code generated by PHP,
First:

echo "This is a string"; 

Will change:

ECHO    'This is a string' 

While

echo 'This is a string'; 

To

 ECHO    'This is a string' 

, Is the same
If yes

echo "This is a $variable"; 

The OPCODE generated by PHP 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 

While

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.