Add optional simplexml mod install test

README.md

@@ -46,6 +46,7 @@ receives the most testing:
     * hash
     * session
     * json
+	* simplexml (This is not strictly necessary, but may result in a better experience.)
     * curl (This is not strictly necessary, but may result in a better experience.)
 
 * MySQL 5.x

config/ampache.cfg.php.dist

@@ -427,7 +427,7 @@ art_order = "db,tags,folder,musicbrainz,lastfm,google"
 ; Set this to true to enable display of similar artists or albums
 ; while browsing. Requires Last.FM.
 ; DEFAULT: false
-show_similar = "true"
+;show_similar = "false"
 
 ; Concerts
 ; Set this to true to enable display of artist concerts

lib/debug.lib.php

@@ -229,6 +229,11 @@ function check_php_zlib()
     return function_exists('gzcompress');
 }
 
+function check_php_simplexml()
+{
+    return function_exists('simplexml_load_string');
+}
+
 function return_bytes($val)
 {
     $val = trim($val);

templates/show_test_table.inc.php

@@ -110,6 +110,15 @@
     <?php echo T_('This tests whether you have the zlib extension enabled. This is not strictly necessary, but may result in a better experience (zip download).'); ?>
     </td>
 </tr>
+<tr>
+    <td valign="top"><?php echo T_('PHP simplexml extension'); ?></td>
+    <td valign="top">
+    <?php echo debug_wresult(check_php_simplexml()); ?>
+    </td>
+    <td>
+    <?php echo T_('This tests whether you have the simplexml extension enabled. This is not strictly necessary, but may result in a better experience.'); ?>
+    </td>
+</tr>
 <tr>
     <td valign="top"><?php echo T_('PHP safe mode disabled'); ?></td>
     <td valign="top">