General: Check to see that the PHP-XML module is enabled before using XML functions.

There are a handful of places where we don't check that the XML functions exist before we use them. Ubuntu's PHP 7 packages don't include PHP-XML by default, increasing the chance of this causing issues.

Props kraftbj, markoheijnen.
Fixes #37122.



git-svn-id: https://develop.svn.wordpress.org/trunk@38883 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/link-parse-opml.php

@@ -72,6 +72,11 @@ function endElement($parser, $tagName) {
 }
 
 // Create an XML parser
+if ( ! function_exists( 'xml_parser_create' ) ) {
+	trigger_error( __( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML extension." ) );
+	wp_die( __( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML extension." ) );
+}
+
 $xml_parser = xml_parser_create();
 
 // Set the functions to handle opening and closing tags

src/wp-includes/IXR/class-IXR-message.php

@@ -44,6 +44,11 @@ class IXR_Message
 
     function parse()
     {
+        if ( ! function_exists( 'xml_parser_create' ) ) {
+            trigger_error( __( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML" ) );
+            return false;
+        }
+
         // first remove the XML declaration
         // merged from WP #10698 - this method avoids the RAM usage of preg_replace on very large messages
         $header = preg_replace( '/<\?xml.*?\?'.'>/s', '', substr( $this->message, 0, 100 ), 1 );

src/wp-includes/atomlib.php

@@ -121,6 +121,11 @@ class AtomParser {
 
         array_unshift($this->ns_contexts, array());
 
+        if ( ! function_exists( 'xml_parser_create_ns' ) ) {
+        	trigger_error( __( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML extension." ) );
+        	return false;
+        }
+
         $parser = xml_parser_create_ns();
         xml_set_object($parser, $this);
         xml_set_element_handler($parser, "start_element", "end_element");

src/wp-includes/feed.php

@@ -538,6 +538,12 @@ function prep_atom_text_construct($data) {
 		return array('text', $data);
 	}
 
+	if ( ! function_exists( 'xml_parser_create' ) ) {
+		trigger_error( __( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML extension." ) );
+
+		return array( 'html', "<![CDATA[$data]]>" );
+	}
+
 	$parser = xml_parser_create();
 	xml_parse($parser, '<div>' . $data . '</div>', true);
 	$code = xml_get_error_code($parser);

src/wp-includes/rss.php

@@ -60,15 +60,13 @@ class MagpieRSS {
 	 */
 	function __construct( $source ) {
 
-		# if PHP xml isn't compiled in, die
+		# Check if PHP xml isn't compiled
 		#
-		if ( !function_exists('xml_parser_create') )
-			trigger_error( "Failed to load PHP's XML Extension. https://secure.php.net/manual/en/ref.xml.php" );
+		if ( ! function_exists('xml_parser_create') ) {
+			return trigger_error( "PHP's XML extension is not available. Please contact your hosting provider to enable PHP's XML extension." );
+		}
 
-		$parser = @xml_parser_create();
-
-		if ( !is_resource($parser) )
-			trigger_error( "Failed to create an instance of PHP's XML parser. https://secure.php.net/manual/en/ref.xml.php");
+		$parser = xml_parser_create();
 
 		$this->parser = $parser;