resolve #27

Allow multi-line emphasis. Fix #28.

Parsedown.php

@@ -678,14 +678,14 @@ class Parsedown
 
 		if (strpos($text, '_') !== FALSE)
 		{
-			$text = preg_replace('/__(?=\S)(.+?)(?<=\S)__/', '<strong>$1</strong>', $text);
+			$text = preg_replace('/__(?=\S)(.+?)(?<=\S)__(?!_)/s', '<strong>$1</strong>', $text);
-			$text = preg_replace('/_(?=\S)(.+?)(?<=\S)_/', '<em>$1</em>', $text);
+			$text = preg_replace('/_(?=\S)(.+?)(?<=\S)_/s', '<em>$1</em>', $text);
 		}
 
 		if (strpos($text, '*') !== FALSE)
 		{
-			$text = preg_replace('/\*\*(?=\S)(.+?)(?<=\S)\*\*/', '<strong>$1</strong>', $text);
+			$text = preg_replace('/\*\*(?=\S)(.+?)(?<=\S)\*\*(?!\*)/s', '<strong>$1</strong>', $text);
-			$text = preg_replace('/\*(?=\S)(.+?)(?<=\S)\*/', '<em>$1</em>', $text);
+			$text = preg_replace('/\*(?=\S)(.+?)(?<=\S)\*/s', '<em>$1</em>', $text);
 		}
 
 		$text = strtr($text, $map);

tests/data/emphasis.html

@@ -5,3 +5,7 @@
 <p>Here's <strong>a strong one that uses underscores</strong>.</p>
 <p>This is not _ one _ neither is * this * neither is _ this_ neither is _this _.</p>
 <p>An empty emphasis ** is not __ an emphasis.</p>
+<p>A <em>multi-line
+emphasis</em></p>
+<p>A <strong>multi-line
+strong emphasis</strong></p>

tests/data/emphasis.md

@@ -11,3 +11,9 @@ Here's __a strong one that uses underscores__.
 This is not _ one _ neither is * this * neither is _ this_ neither is _this _.
 
 An empty emphasis ** is not __ an emphasis.
+
+A *multi-line
+emphasis*
+
+A **multi-line
+strong emphasis**

tests/data/emphasis_-_em_strong.html

@@ -0,0 +1,5 @@
+<p><strong><em>em strong</em></strong></p>
+<p><strong><em>one</em> at the start</strong></p>
+<p><strong>one at the <em>end</em></strong></p>
+<p><strong>one <em>in the</em> middle</strong></p>
+<p><strong>one with <em>asterisks</em></strong></p>

tests/data/emphasis_-_em_strong.md

@@ -0,0 +1,9 @@
+___em strong___
+
+___one_ at the start__
+
+__one at the _end___
+
+__one _in the_ middle__
+
+**one with *asterisks***