Document variable properties.

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@288221 c90b9560-bf6c-de11-be94-00142212c4b1

language/types/string.xml

@@ -646,6 +646,34 @@ echo "I'd like to have another {${ strrev('reeb') }}, hips";
  -->
      </programlisting>
     </informalexample>
+
+    <para>
+     It is also possible to access class properties using variables
+     within strings using this syntax.
+    </para>
+
+   <informalexample>
+    <programlisting role="php">
+<![CDATA[
+<?php
+class foo {
+    var $bar = 'I am bar.';
+}
+
+$foo = new foo();
+$bar = 'bar';
+$baz = array('foo', 'bar', 'baz', 'quux');
+echo "{$foo->$bar}\n";
+echo "{$foo->$baz[1]}\n";
+?>
+]]>
+    </programlisting>
+   &example.outputs;
+   <screen>
+I am bar.
+I am bar.
+   </screen>
+   </informalexample>
     
     <note>
      <para>

language/variables.xml

@@ -721,9 +721,46 @@ echo "$a $hello";
     wanted <varname>$$a</varname> as the variable and then the [1]
     index from that variable.  The syntax for resolving this ambiguity
     is: <varname>${$a[1]}</varname> for the first case and
-    <varname>${$a}[1]</varname> for the second.
+    <varname>${$a}[1]</varname> for the second. 
    </simpara>
-   
+
+   <simpara>
+    Class properties may also be accessed using variable property
+    names. The variable property name will be resolved within the
+    scope from which the call is made. For instance, if you have an
+    expression such as <varname>$foo->$bar</varname>, then the local
+    scope will be examined for <varname>$bar</varname> and its value
+    will be used as the name of the property
+    of <varname>$foo</varname>. This is also true
+    if <varname>$bar</varname> is an array access.
+   </simpara>
+
+   <para>
+    <example>
+     <title>Variable function example</title>
+      <programlisting role="php">
+<![CDATA[
+<?php
+class foo {
+    var $bar = 'I am bar.';
+}
+
+$foo = new foo();
+$bar = 'bar';
+$baz = array('foo', 'bar', 'baz', 'quux');
+echo $foo->$bar . "\n";
+echo $foo->$baz[1] . "\n";
+?>
+]]>
+     </programlisting>
+     &example.outputs;
+     <screen>
+I am bar.
+I am bar.
+     </screen>
+    </example>
+   </para>
+
    <warning>
     <simpara>
      Please note that variable variables cannot be used with PHP's