Howdy

you can use a reference parameter to accumulate values like this.

function read_array($in, &$accumulator) {

    $out = array();

    foreach(file($in) as $str) {

        $str = trim($str);
  
        //some modifications

        $out[] = $str;
        //OR $all_str .= $str
        $accumulator[] = $str;
        // or $accumulator .= $str;
    }

    return $out;
}

Now after you call the function the last parameter will hold all of the new values, this is a nasty way though and I would suggest you read some more about references(http://au2.php.net/manual/en/language.references.php).
You can ofcourse use a global variable to store this aswell if it was an OO based thing (don`t use global keyword if your not using OO dear god please!).
+1 for marking this as bogus, bad programming practice should not a language make :)

I know about references. Reference parameter it's the same like internal variable. I suggest new operator. And if we will use it - we will not need to define and use any variables.

What you want is fundamentally wrong and the wrong way to look at it, having some sort of vahalla of acumulating data would be slow, bloated and incredibly inflexible.
So to get the facts straight, you don`t want to define 1 extra variable because your lazy and then request a language feature to support your aversion to doing the right thing ?

Oh just thought of something, you can always use ob_start and friends it's a global buffer of sorts or you can always just define your own.

There is no real need for such a syntax.