Why a full stop, “.” and not a plus symbol, “+”, for string concatenation in PHP?

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

Answer 1

This doesn't answer the question, just wanted to share something.

From PHP Manual: String Operators, someone posted this which I find rather interesting. Notice how the space plays a part in the output.

Excerpt:
If you attempt to add numbers with a concatenation operator, your result will be the result of those numbers as strings.

<?php

echo "thr"."ee";           //prints the string "three"
echo "twe" . "lve";        //prints the string "twelve"
echo 1 . 2;                //prints the string "12"
echo 1.2;                  //prints the number 1.2
echo 1+2;                  //prints the number 3

?>

Answer 2

I am not a PHP expert, but, how else do you do differentiate that last two lines?

$first  = 100;
$second = 20;
$stringresult     = $first . $second; // "10020"
$arithmeticresult = $first + $second; // 120

Answer 3

Here is a bit of historical context.

• The PHP language started out as a set of Perl scripts.
• As such, PHP gets most of it's syntax from Perl.

• Perl, and by extension PHP, has untyped variables.

       "5"  ==   5
  "5" + 5   ==  10
  "5" . 5   ==  55
  

• To be able to tell the difference between addition and concatenation, they had to be two different operators.
• Perl copied the method access operator from C ->.
• This was before many of the more modern programming languages started to use . for method access.
• Concatenation is one of the more common operations, and should use fewer characters. According to Huffman coding.
• . was one of the few characters available for this use. The only other one that would make sense to use is ~, which is probably why that is now the Perl 6 concatenation operator.

Answer 4

PHP's syntax is influenced by Perl, and . is the string concatenation operator in Perl.

In a weakly typed language there are advantages to having a different string concatenation and numeric addition operators: which one you use will influence which type the language coerces the variables to.

As it happens, Perl 6 will use a tilde ~ instead of a dot . for string concatenation, because . will be used for object member access. So it seems the designers of Perl now think it was a bad choice.

Perhaps, in Perl and PHP's early, non-Object-Oriented days, it seemed like as good a choice as any. Maybe the designers of both languages never envisaged them becoming strong OO languages.

As for whether PHP will one day ditch its -> member access syntax for ., who knows?

Answer 5

I guess it is so you can concatenate numbers with strings?

$i=100;
$str="hello";
$str2 = $str.$i

Since you don't declare variable types, with a + it could give a result of 100 instead of "hello100."

Answer 6

Douglas Crockford thinks that + for Concatenation is a Bad Idea:

JavaScript has its share of design errors, such as the overloading of + to mean both addition and concatenation with type coercion