What is the difference between echo with braces and without braces, and why do both methods exist? [closed]

Question

The question is in the title.

I think most of us that program in php learned to echo "string";. While common, I am wondering why we use this so different then any other function.

So why do we:

echo "Some String";

Instead of

echo("Some String");

And why do both exist and behave differently? Is there any reference to why this choice was made?

Edit: I see my question being flooded with both downvotes and upvotes. Please be constructive when voting either way.

People refer to the php docs stating that echo is a language construct and therefor is used differently. But in that case, since we can both use it as a construct aswell as functional: which is the preferred method? And why was it implemented both ways while it should only be a language construct?

Edit 2: The same as above pretty much counts for require, require_once, include and include_once. I can't find anything on the web explaining -why- these constructs were also implemented functional (and in the case of echo(), in a flawed way).

Answer 1

From php.net:

echo is not actually a function (it is a language construct), so you are not required to use parentheses with it.

---

if you want to pass more than one parameter to echo, the parameters must not be enclosed within parentheses.

Example (as of PHP 5.4.14):

<?php
header('Content-Type: text/plain');

echo(1);        // < works fine

echo(1, 2, 3);  // < Parse error: syntax error, unexpected ',' on line 6

echo 1;         // < works fine

echo 1, 2, 3;   // < works fine
?>

---

UPDv1:

Note: Because this is a language construct and not a function, it cannot be called using variable functions.

<?php
header('Content-Type: text/plain');

$print = 'print_r';
$print(1);      // < works fine

$echo = 'echo';
$echo(1);       // < Fatal error: Call to undefined function echo() on line 8
?>

---

UPDv2:

As of include (same applies to require, require_once and include_once), it might have a return value. For example:

fileA.php:

<?php return 1; ?>

fileB.php:

<?php return 'abc'; ?>

Test:

<?php
header('Content-Type: text/plain');

echo (include 'fileA.php'); // one way
echo PHP_EOL;
echo include('fileB.php');  // another way
?>

Shows:

1
abc

It was mentioned on php.net in examples #4 and #5.

Because expressions like include 'fileA.php' == 'OK' are not obvious (according to operator precedence), you should enclose them in parentheses, or use "function-like" approach: (include 'fileA.php') == 'OK' or include('fileA.php') == 'OK'.

Answer 2

From the PHP docs

echo is not actually a function (it is a language construct), so you are not required to use parentheses with it. echo (unlike some other language constructs) does not behave like a function, so it cannot always be used in the context of a function. Additionally, if you want to pass more than one parameter to echo, the parameters must not be enclosed within parentheses

It's not a funcion, hence no parenthesis