PHP hidden trick or a supported feature?

Question

I know that to concatenate strings in php, a dot should be used:

echo 'hello' . ' world'; // hello world

But incidentally i typed this:

echo 'hello' , ' world';

and the result was still hello world without any errors.

Why is it so? Can we also concatenate using comma?

Answer 1

It's documented in the entry for echo:

void echo ( string $arg1 [, string $... ] )

The two forms are not actually equivalent, since there's a difference in the instant in which functions are evaluated.

Answer 2

No, you cannot concatenate with comma:

<?php

$foo = 'One', 'Two';

?>

Parse error: syntax error, unexpected ','

Answer 3

echo is a language construct, so you don't need parenthesis. But you are "passing" multiple parameters to echo. Think of it as:

echo('hello', ' world');

Answer 4

It's no hidden trick, it's just how echo works. If you have a look at the PHP reference docs for echo, you'll notice that it will echo the list of strings that you throw at it.

Answer 5

echo is a language construct. It is in someway a special function that's defined at Grammar level (I might be wrong on this). It is a function that somehow doesn't follow any of the defined way of defining a function/method as an example and the way of calling them. It "by-passes" some syntax check :)

There's a nice post discussing the difference between language construct & built in functions here in StackOverflow.

Answer 6

echo('hello', ' world');

It's the same as:

echo 'hello', ' world';