Question

Why did the designers of PHP decide to use a full stop / period / “.” as the string
concatenation operator rather than the more usual plus symbol “+” ?

Is there any advantage to it, or any reason at all? Or did they just like to? :o)

Answer 1

The most obvious reason would probably be that PHP inherits a lot of its syntax from Perl – and Perl uses a dot (.) for string concatenation.

But, we can delve deeper into it and figure out why this was implemented in Perl – the + operator is most commonly used for mathematical equations – it’s only used for concatenation in languages in which the variable type can define the way in which the operator works (simple explanation, example is C#)

var intAddition = 1 + 2;
Console.WriteLine(intAddition); // Prints 3
var stringConcat = "1" + "2";
Console.WriteLine(stringConcat); // Prints "12"

^ As you can see, the + operator is used both for concatenation and addition in C#.

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Perhaps the reasoning goes lower level and is due to the boolean algebra of logic gates – + means OR in logic gates, whereas . is used as the AND operator – which makes sense when it comes to string concatenation.

It makes sense to have two separate operators, one for concatenation and one for addition – it’s just unfortunate that these two can be mixed up due to other languages.