diff --git a/CHANGES.md b/CHANGES.md
index aed414f091..e46b22fe81 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -11,6 +11,7 @@ New Grammars:
 
 Grammars:
 
+- enh(xml) support processing instructions (#3492) [Josh Goebel][]
 - enh(ruby ) better support multi-line IRB prompts
 - enh(bash) improved keyword `$pattern` (numbers allowed in command names) [Martin Mattel][]
 - add `meta.prompt` scope for REPL prompts, etc [Josh Goebel][]
diff --git a/src/languages/php.js b/src/languages/php.js
index 9dfa2fb3b3..f0e5f8ef68 100644
--- a/src/languages/php.js
+++ b/src/languages/php.js
@@ -29,11 +29,10 @@ export default function(hljs) {
   const PREPROCESSOR = {
     scope: 'meta',
     variants: [
-      {
-        begin: /<\?php/,
-        relevance: 10
-      }, // boost for obvious PHP
-      { begin: /<\?[=]?/ },
+      { begin: /<\?php/, relevance: 10 }, // boost for obvious PHP
+      { begin: /<\?=/ },
+      // less relevant per PSR-1 which says not to use short-tags
+      { begin: /<\?/, relevance: 0.1 },
       { begin: /\?>/ } // end php tag
     ]
   };
diff --git a/src/languages/xml.js b/src/languages/xml.js
index 971bc9cba7..cb640d8a1e 100644
--- a/src/languages/xml.js
+++ b/src/languages/xml.js
@@ -122,11 +122,23 @@ export default function(hljs) {
         relevance: 10
       },
       XML_ENTITIES,
+      // xml processing instructions
       {
         className: 'meta',
-        begin: /<\?xml/,
         end: /\?>/,
-        relevance: 10
+        variants: [
+          {
+            begin: /<\?xml/,
+            relevance: 10,
+            contains: [
+              QUOTE_META_STRING_MODE
+            ]
+          },
+          {
+            begin: /<\?[a-z][a-z0-9]+/,
+          }
+        ]
+
       },
       {
         className: 'tag',
diff --git a/test/markup/xml/namespace.expect.txt b/test/markup/xml/namespace.expect.txt
index 4317227c5f..05aaa944e8 100644
--- a/test/markup/xml/namespace.expect.txt
+++ b/test/markup/xml/namespace.expect.txt
@@ -1,3 +1,3 @@
-<span class="hljs-meta">&lt;?xml version=&quot;1.0&quot; encoding=&quot;ISO-8859-1&quot; ?&gt;</span>
+<span class="hljs-meta">&lt;?xml version=<span class="hljs-string">&quot;1.0&quot;</span> encoding=<span class="hljs-string">&quot;ISO-8859-1&quot;</span> ?&gt;</span>
 <span class="hljs-tag">&lt;<span class="hljs-name">xs:schema</span> <span class="hljs-attr">xmlns:xs</span>=<span class="hljs-string">&quot;http://www.w3.org/2001/XMLSchema&quot;</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">xs:schema</span>&gt;</span>
 <span class="hljs-tag">&lt;<span class="hljs-name">s:schema</span> <span class="hljs-attr">xmlns:s</span>=<span class="hljs-string">&quot;http://www.w3.org/2001/XMLSchema&quot;</span>&gt;</span><span class="hljs-tag">&lt;/<span class="hljs-name">s:schema</span>&gt;</span>
diff --git a/test/markup/xml/processing.expect.txt b/test/markup/xml/processing.expect.txt
new file mode 100644
index 0000000000..19018d0d0b
--- /dev/null
+++ b/test/markup/xml/processing.expect.txt
@@ -0,0 +1,6 @@
+<span class="hljs-meta">&lt;?xml version=<span class="hljs-string">&quot;1.0&quot;</span> encoding=<span class="hljs-string">&quot;ISO-8859-1&quot;</span> ?&gt;</span>
+<span class="hljs-meta">&lt;?PITarget PIContent?&gt;</span>
+<span class="hljs-meta">&lt;?xml-stylesheet type=<span class="hljs-string">&quot;text/xsl&quot;</span> href=<span class="hljs-string">&quot;style.xsl&quot;</span>?&gt;</span>
+<span class="hljs-meta">&lt;?xml-stylesheet type=<span class="hljs-string">&quot;text/css&quot;</span> href=<span class="hljs-string">&quot;style.css&quot;</span>?&gt;</span>
+Some <span class="hljs-meta">&lt;?Pub _font FontColor=&quot;green&quot;?&gt;</span>green<span class="hljs-meta">&lt;?Pub /_font?&gt;</span> text.
+<span class="hljs-meta">&lt;?mso-application progid=&quot;Excel.Sheet&quot;?&gt;</span>
diff --git a/test/markup/xml/processing.txt b/test/markup/xml/processing.txt
new file mode 100644
index 0000000000..e9565dd387
--- /dev/null
+++ b/test/markup/xml/processing.txt
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="ISO-8859-1" ?>
+<?PITarget PIContent?>
+<?xml-stylesheet type="text/xsl" href="style.xsl"?>
+<?xml-stylesheet type="text/css" href="style.css"?>
+Some <?Pub _font FontColor="green"?>green<?Pub /_font?> text.
+<?mso-application progid="Excel.Sheet"?>