A simple summary of the difference between single and double quotes in PHP strings, PHP string _php Tutorial

A simple summary of the difference between single and double quotes in PHP strings, PHP string

Today, a friend asked, said the difference, by the way review.

Single and double quotation marks are different:

• The fields inside the double quotation mark are interpreted by the compiler and then output as HTML code.
• "The single quotation mark does not explain, the direct output."
• Single quotation marks are resolved more quickly than double quotes.
• Single quotes support \ Escape characters, and double quotes support more escape characters.

$hello = 3;echo "Hello is $hello"; Print Result: Hello is 3 echo ' Hello is $hello '; Print Result: Hello is $hello echo "Hello is $hello \ n"; Print Result: Hello is 2 (simultaneous newline) echo ' Hello is $hello \ n '; Print Result: Hello is $hello \ n

Ps:
Today I saw a foreigner mentioning the single quotation mark of PHP, which mentions something interesting, excerpt from the following:
which says PHP extension Vulcan Logic disassembler, you can see the PHP generated intermediate code,
The first is:

Will change to:

ECHO    

and

It becomes

ECHO    

, is the same
If it is

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      

and

will become

CONCAT    ~0 ' This is a '!0 2 ECHO      

Can see, the speed is much faster, with. Connect the words

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