Document deprecation of undefined constant as bare string fallback

Cf. <https://wiki.php.net/rfc/deprecate-bareword-strings>.

git-svn-id: http://svn.php.net/repository/phpdoc/en@345953 c90b9560-bf6c-de11-be94-00142212c4b1

Author: cmb

trunk/language/constants.xml

@@ -100,9 +100,12 @@ define("__FOO__", "something");
    <simpara>
     If you use an undefined constant, PHP assumes that you mean
     the name of the constant itself, just as if you called it as
-    a <type>string</type> (CONSTANT vs "CONSTANT").  An error of level
-    <link linkend="ref.errorfunc">E_NOTICE</link> will be issued
-    when this happens.  See also the manual entry on why 
+    a <type>string</type> (CONSTANT vs "CONSTANT"). 
+    This fallback is deprecated as of PHP 7.2.0, and an error of level
+    <constant>E_WARNING</constant> is issued when it happens
+    (previously, an error of level
+    <link linkend="ref.errorfunc">E_NOTICE</link> has been issued instead.)
+    See also the manual entry on why 
     <link linkend="language.types.array.foo-bar">$foo[bar]</link> is
     wrong (unless you first <function>define</function>
     <literal>bar</literal> as a constant). This does not apply to <link

trunk/language/types/array.xml

@@ -574,6 +574,13 @@ echo $foo[bar];
     constant named <constant>bar</constant>, then PHP will substitute in the
     <type>string</type> <literal>'bar'</literal> and use that.
    </para>
+   <warning>
+    <simpara>
+     The fallback to treat an undefined constant as bare string is deprecated as
+     of PHP 7.2.0, and issues an error of level <constant>E_WARNING</constant>.
+     Formerly, an error of level <constant>E_NOTICE</constant> has been issued.
+    </simpara>
+   </warning>
 
    <note>
     <simpara>