php_uname() now throws ValueError (#3969)

* `php_uname()` now throws `ValueError`

* Be even more explicit about what 'a' means

Author: jimwins

reference/info/functions/php-uname.xml

@@ -40,10 +40,18 @@
        information is returned:
        <itemizedlist>
         <listitem>
-         <simpara>
-          <literal>'a'</literal>: This is the default. Contains all modes in
-          the sequence <literal>"s n r v m"</literal>.
-         </simpara>
+         <para>
+          <literal>'a'</literal>: This is the default. Returns the same
+          information as the individual modes
+          <simplelist type="inline">
+           <member><literal>'s'</literal></member>
+           <member><literal>'n'</literal></member>
+           <member><literal>'r'</literal></member>
+           <member><literal>'v'</literal></member>
+           <member><literal>'m'</literal></member>
+          </simplelist>
+          separated by spaces.
+         </para>
         </listitem>
         <listitem>
          <simpara>
@@ -89,6 +97,29 @@
   </para>
  </refsect1>
 
+ <refsect1 role="changelog">
+  &reftitle.changelog;
+  <informaltable>
+   <tgroup cols="2">
+    <thead>
+     <row>
+      <entry>&Version;</entry>
+      <entry>&Description;</entry>
+     </row>
+    </thead>
+    <tbody>
+     <row>
+      <entry>8.4.0</entry>
+      <entry>
+       Throws a <classname>ValueError</classname> when an invalid
+       <parameter>mode</parameter> is specified.
+      </entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </informaltable>
+ </refsect1>
+
  <refsect1 role="examples">
   &reftitle.examples;
   <para>