Fix #77100: Inconsistent behavior between constants and magic constants

git-svn-id: http://svn.php.net/repository/phpdoc/en@345954 c90b9560-bf6c-de11-be94-00142212c4b1

Author: cmb

trunk/language/constants.xml

@@ -18,6 +18,11 @@
    expression, it would be expressed thusly:
    <code>[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*</code>
   </para>
+  <para>
+   It is possible to <function>define</function> constants with reserved or even
+   invalid names, whose value can (only) be retrieved with
+   <function>constant</function>. However, doing so is not recommended.
+  </para>
   &tip.userlandnaming;
   <para>
    <example>

trunk/reference/misc/functions/define.xml

@@ -29,6 +29,13 @@
       <para>
        The name of the constant.
       </para>
+      <note>
+       <para>
+        It is possible to <function>define</function> constants with reserved or
+        even invalid names, whose value can (only) be retrieved with
+        <function>constant</function>. However, doing so is not recommended.
+       </para>
+      </note>
      </listitem>
     </varlistentry>
     <varlistentry>
@@ -139,6 +146,37 @@ echo ANIMALS[1]; // outputs "cat"
     </programlisting>
    </example>
   </para>
+  <para>
+   <example>
+    <title>Constants with Reserved Names</title>
+    <para>
+     This example illustrates the <emphasis>possibility</emphasis> to define a
+     constant with the same name as a
+     <link linkend="language.constants.predefined">magic constant</link>.
+     Since the resulting behavior is obviously confusing, it is not recommended
+     to do this in practise, though.
+    </para>
+    <programlisting role="php">
+<![CDATA[
+<?php
+var_dump(defined('__LINE__'));
+var_dump(define('__LINE__', 'test'));
+var_dump(constant('__LINE__'));
+var_dump(__LINE__);
+?>
+]]>
+    </programlisting>
+   &example.outputs;
+   <screen>
+<![CDATA[
+bool(false)
+bool(true)
+string(4) "test"
+int(5)
+]]>
+   </screen>
+   </example>
+  </para>
  </refsect1>
 
  <refsect1 role="seealso">