[PHP] Difference between single quotation and double quotation

Sep 7, 2020 PHP beginner programming study diary

#Programming study diary September 7, 2020 I use single quotation and double quotation in the same situation, but I will summarize what the difference actually is.

#Feature Single quotation: Treat the contents as a character string (handle variables and control character strings as just a character string) Double quotation: Treats the contents as a character string, but treats variables and control character strings as the original source

Since all single quotations are treated as character strings, single quotations are faster.

#Difference in speed When outputting a simple character string as shown below, the output content is the same.

//Double quotation
echo "Hello World";
echo'<br>';

// single quote
echo'Hello World';

Hello World
Hello World

As mentioned at the beginning, the operation processing speed is single quotation » double quotation </ font> when using variable expansion and when variable is simply assigned. (There is a difference of about 1.2 to 2 times) However, there is not much difference in speed between the case of character string concatenation and the case of character string comparison.

#Difference in operation It was described at the beginning that the handling of variables and control character strings is different, but it will be explained using a concrete example. Control strings are characters used to perform special controls other than characters such as newlines (\ n) and empty strings (nil). As shown in the specific example below, in the case of single quotation, the control character string and variables are output as they are as a character string. The double quotation is output as it is as the contents of the variable or the control character string.

$ str = "World";

echo'Hello $ str';
echo "Hello $ str";
echo "Hello {$ str}";

echo'Hello World \ n';
echo "Hello World \ n";

Hello $ str
Hello World
Hello World
Hello World \ n
Hello World (new line on display)

#Summary Although it is a small system, it is faster to use single quotation. (For large systems, it makes a big difference) Basically, use single quotations, and use double quotations when necessary (variable expansion, etc.).

#References [PHP]'(single quotation) or “(double quotation) should be used (PHP acceleration) Difference between double quotation and single quotation