In 
http://www.php.net/manual/en/language.types.type-juggling.php
there's a sample:

$a = 1;       // $a is an integer
$a[0] = "f";  // $a becomes an array, with $a[0] holding "f"

Which will issue an warning:

Warning:  Cannot use a scalar value as an array in cast.php on line 3

and $a is still a int(1).
Tried PHP 4.2.3 under Windows and PHP 4.0.6 under Linux with same result.

And in
http://www.php.net/manual/en/language.types.string.php
inside the Heredoc warning it said:

Probably the nastiest gotcha is that there may also not be a carriage return (\r) at the end of the line, only a form feed, AKA newline (\n). Since Microsoft Windows uses the sequence \r\n as a line terminator, your heredoc may not work if you write your script in a Windows editor. However, most programming editors provide a way to save your files with a UNIX line terminator. 

Which is actually not true.  PHP 4 seems working fine with Windows line terminator in Heredoc syntax.  Also tried PHP 4.2.3 under Windows and PHP 4.0.6 under Linux, they both work correctly without any problem.