- empty clarified, noted it is a language construct

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@47588 c90b9560-bf6c-de11-be94-00142212c4b1

functions/var.xml

@@ -48,13 +48,26 @@ print $double_value_of_var; // prints 122.34343
     <title>Description</title>
     <funcsynopsis>
      <funcprototype>
-      <funcdef>int <function>empty</function></funcdef>
+      <funcdef>boolean <function>empty</function></funcdef>
       <paramdef>mixed <parameter>var</parameter></paramdef>
      </funcprototype>
     </funcsynopsis>
+    <note>
+     <para>
+      <function>empty</function> is a language construct.
+     </para>
+    </note>
     <para>
-     Returns false if <parameter>var</parameter> is set and has a
-     non-empty or non-zero value; true otherwise.
+     This is the opposite of 
+     <literal>(boolean) <parameter>var</parameter></literal>,
+     exept that no warning is generated when the variable is not set.
+     See <link linkend="language.types.boolean.casting">converting 
+     to boolean</link> for more information.
+    </para>
+     
+    <!-- Returns false if <parameter>var</parameter> is set and has a
+     non-empty or non-zero value; true otherwise. -->
+     
      <informalexample>
       <programlisting role="php">
 $var = 0;
@@ -68,12 +81,13 @@ if (!isset($var)) { // evaluates false
 }
       </programlisting>
      </informalexample>
-    </para>
+
     <simpara>
      Note that this is meaningless when used on anything which isn't a
      variable; i.e. <command>empty (addslashes ($name))</command> has
      no meaning since it would be checking whether something which
      isn't a variable is a variable with a false value.
+     <!-- will even result in parse error (at least in PHP 4) -->
     </simpara>
     <simpara>
      See also <function>isset</function> and
@@ -103,7 +117,7 @@ if (!isset($var)) { // evaluates false
      Possibles values for the returned string are:
      <itemizedlist>
       <listitem>
-       <simpara>"boolean"</simpara>
+       <simpara>"boolean" (since PHP 4)</simpara>
       </listitem>
       <listitem>
        <simpara>"integer"</simpara>
@@ -121,13 +135,16 @@ if (!isset($var)) { // evaluates false
        <simpara>"object"</simpara>
       </listitem>
       <listitem>
-       <simpara>"resource"</simpara>
+       <simpara>"resource" (since PHP 4)</simpara>
+      </listitem>
+      <listitem>
+       <simpara>"NULL" (since PHP 4)</simpara>
       </listitem>
       <listitem>
        <simpara>"user function" (PHP 3 only, deprecated)</simpara>
       </listitem>
       <listitem>
-       <simpara>"unknown type"</simpara>
+       <simpara>"unknown type"<!-- someone's joking? --></simpara>
       </listitem>
      </itemizedlist>
     </para>