zendframework/zf2-documentation — pull request #1411 by andy-b-84 (2014-12-09 15:26:30+00:00)
Title: bugfix in using HEREDOC syntax

you cannot write anything else than the string identifier, when you want to end it.
As seen in this exemple :
andy@plaxton-mint ~/workspace/zf2/public (master %) $ php -a
Interactive mode enabled

php > $a = (<< zeiuzeyf zeiuzef
<<< > zerferf
<<< > erfefer
<<< > freferf
<<< > erfrefr
<<< > A);
<<< > A
php ( );
php > echo $a;
zeiuzeyf zeiuzef
zerferf
erfefer
freferf
erfrefr
A);php >

see http://php.net/manual/fr/language.types.string.php#language.types.string.syntax.heredoc for more details