What is the difference between ' and " in PHP? [duplicate]

Answer 1

There are 3 syntax used to declare strings, in PHP <= 5.2 :

• single quoted
• double quoted
• heredoc

With single quotes :

variables and escape sequences for special characters will not be expanded

For instance :

echo 'Variables do not $expand $either';

Will output :

Variables do not $expand $either

With double-quotes :

The most important feature of double-quoted strings is the fact that variable names will be expanded.

For instance :

$a = 10;
echo "a is $a";

Will output :

a is 10

And, with heredoc :

Heredoc text behaves just like a double-quoted string, without the double quotes. This means that quotes in a heredoc do not need to be escaped,

For instance :

$a = 10;
$b = 'hello';

$str = <<

Will get you :

a is 10
and "b" is hello.