Implement user notes: use isset for variables, see also function_exists, and

make it clear the importance of passing in a string.  Also some minor fixes.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@130822 c90b9560-bf6c-de11-be94-00142212c4b1

reference/misc/functions/defined.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.3 $ -->
+<!-- $Revision: 1.4 $ -->
 <!-- splitted from ./en/functions/misc.xml, last change in rev 1.2 -->
   <refentry id="function.defined">
    <refnamediv>
@@ -18,23 +18,35 @@
      Returns &true; if the named constant given by
      <parameter>name</parameter> has been defined, 
      &false; otherwise.
-      <example>
+    </para>
+    <para>
+     <example>
       <title>Checking Constants</title>
       <programlisting role="php">
 <![CDATA[
 <?php
-if (defined("CONSTANT")){ // Note that it should be quoted
+// Note the use of quotes, this is important.  This example is checking 
+// if the string 'CONSTANT' is the name of a constant named CONSTANT 
+if (defined('CONSTANT')) {
     echo CONSTANT;
-    }
+}
 ?>
 ]]>
       </programlisting>
      </example>
     </para>
+    <note>
+     <para>
+      If you're wanting to see if a variable exists, use 
+      <function>isset</function> as <function>defined</function> only
+      applies to <link linkend="language.constants">constants</link>.
+     </para>
+    </note>
     <para>
      See also <function>define</function>,
      <function>constant</function>,
-     <function>get_defined_constants</function> and the section on
+     <function>get_defined_constants</function>, 
+     <function>function_exists</function>, and the section on
      <link linkend="language.constants">Constants</link>.
     </para>
    </refsect1>