diff --git a/bin/create-php-parser.js b/bin/create-php-parser.js
index fda773d0dd3f0c..f5cd5327fd0008 100755
--- a/bin/create-php-parser.js
+++ b/bin/create-php-parser.js
@@ -14,6 +14,7 @@ const parser = pegjs.generate(
 		phpegjs: {
 			parserNamespace: null,
 			parserGlobalNamePrefix: 'Gutenberg_PEG_',
+			mbstringAllowed: false,
 		},
 	}
 );
diff --git a/docs/faq.md b/docs/faq.md
index 21c2115c243da5..efa82e7401bc88 100644
--- a/docs/faq.md
+++ b/docs/faq.md
@@ -119,14 +119,13 @@ This also <a href="https://github.com/WordPress/gutenberg/issues/1516">gives us
 In JS:
 
 ```js
-wp.blocks.parse( postContent );
+var blocks = wp.blocks.parse( postContent );
 ```
 
 In PHP:
 
 ```php
-$parser = new Gutenberg_PEG_Parser;
-$blocks = $parser->parse( $post_content );
+$blocks = gutenberg_parse_blocks( $post_content );
 ```
 ## Why should I start using this once released?
 Blocks are likely to become the main way users interact with content. Users are going to be discovering functionality in the new universal inserter tool, with a richer block interface that provides more layout opportunities.
diff --git a/gutenberg.php b/gutenberg.php
index fd37d4b9354989..fa2af8f5b77dbc 100644
--- a/gutenberg.php
+++ b/gutenberg.php
@@ -18,6 +18,7 @@
 	// Load API functions, register scripts and actions, etc.
 	require_once dirname( __FILE__ ) . '/lib/blocks.php';
 	require_once dirname( __FILE__ ) . '/lib/client-assets.php';
+	require_once dirname( __FILE__ ) . '/lib/compat.php';
 	require_once dirname( __FILE__ ) . '/lib/i18n.php';
 	require_once dirname( __FILE__ ) . '/lib/parser.php';
 	require_once dirname( __FILE__ ) . '/lib/register.php';
diff --git a/lib/blocks.php b/lib/blocks.php
index b86eb1cd7b41c6..a8229bea915dae 100644
--- a/lib/blocks.php
+++ b/lib/blocks.php
@@ -70,25 +70,30 @@ function unregister_block_type( $name ) {
 }
 
 /**
- * Renders the dynamic blocks into the post content
+ * Parses blocks out of a content string.
  *
- * @since 0.1.0
+ * @since 0.5.0
  *
  * @param  string $content Post content.
+ * @return array  Array of parsedblock objects.
+ */
+function gutenberg_parse_blocks( $content ) {
+	$parser = new Gutenberg_PEG_Parser;
+	return $parser->parse( _gutenberg_utf8_split( $content ) );
+}
+
+/**
+ * Parses dynamic blocks out of `post_content` and re-renders them.
  *
+ * @since 0.1.0
+ *
+ * @param  string $content Post content.
  * @return string          Updated post content.
  */
 function do_blocks( $content ) {
 	global $wp_registered_blocks;
 
-	if ( ! extension_loaded( 'mbstring' ) ) {
-		// Skip server-side rendering of blocks until WordPress/gutenberg#1611
-		// is properly fixed.
-		return $content;
-	}
-
-	$parser = new Gutenberg_PEG_Parser;
-	$blocks = $parser->parse( $content );
+	$blocks = gutenberg_parse_blocks( $content );
 
 	$content_after_blocks = '';
 
diff --git a/lib/compat.php b/lib/compat.php
new file mode 100644
index 00000000000000..d6e69c2052c1a3
--- /dev/null
+++ b/lib/compat.php
@@ -0,0 +1,69 @@
+<?php
+/**
+ * PHP configuration compatibility functions for the Gutenberg editor plugin.
+ *
+ * @package gutenberg
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	die( 'Silence is golden.' );
+}
+
+/**
+ * Splits a UTF-8 string into an array of UTF-8-encoded codepoints.
+ *
+ * @since 0.5.0
+ *
+ * Based on WordPress' _mb_substr() compat function.
+ *
+ * @param string $str        The string to split.
+ * @return array
+ */
+function _gutenberg_utf8_split( $str ) {
+	if ( _wp_can_use_pcre_u() ) {
+		// Use the regex unicode support to separate the UTF-8 characters into
+		// an array.
+		preg_match_all( '/./us', $str, $match );
+		return $match[0];
+	}
+
+	$regex = '/(
+		  [\x00-\x7F]                  # single-byte sequences   0xxxxxxx
+		| [\xC2-\xDF][\x80-\xBF]       # double-byte sequences   110xxxxx 10xxxxxx
+		| \xE0[\xA0-\xBF][\x80-\xBF]   # triple-byte sequences   1110xxxx 10xxxxxx * 2
+		| [\xE1-\xEC][\x80-\xBF]{2}
+		| \xED[\x80-\x9F][\x80-\xBF]
+		| [\xEE-\xEF][\x80-\xBF]{2}
+		| \xF0[\x90-\xBF][\x80-\xBF]{2} # four-byte sequences   11110xxx 10xxxxxx * 3
+		| [\xF1-\xF3][\x80-\xBF]{3}
+		| \xF4[\x80-\x8F][\x80-\xBF]{2}
+	)/x';
+
+	// Start with 1 element instead of 0 since the first thing we do is pop.
+	$chars = array( '' );
+	do {
+		// We had some string left over from the last round, but we counted it
+		// in that last round.
+		array_pop( $chars );
+
+		// Split by UTF-8 character, limit to 1000 characters (last array
+		// element will contain the rest of the string).
+		$pieces = preg_split(
+			$regex,
+			$str,
+			1000,
+			PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY
+		);
+
+		$chars = array_merge( $chars, $pieces );
+
+		// If there's anything left over, repeat the loop.
+		if ( count( $pieces ) > 1 ) {
+			$str = array_pop( $pieces );
+		} else {
+			break;
+		}
+	} while ( $str );
+
+	return $chars;
+}
diff --git a/lib/parser.php b/lib/parser.php
index 2ae0b369a9385b..ad4fa1631b717c 100644
--- a/lib/parser.php
+++ b/lib/parser.php
@@ -6,38 +6,65 @@
  */
 
 
-/* Usefull functions: */
+/* Useful functions: */
 
 /* Gutenberg_PEG_chr_unicode - get unicode character from its char code */
-if (!function_exists('Gutenberg_PEG_chr_unicode')) { function Gutenberg_PEG_chr_unicode($code) { return mb_convert_encoding('&#' . $code . ';', 'UTF-8', 'HTML-ENTITIES');} }
-/* Gutenberg_PEG_peg_regex_test - multibyte regex test */
-if (!function_exists('Gutenberg_PEG_peg_regex_test')) { function Gutenberg_PEG_peg_regex_test($pattern, $string) { if (substr($pattern, -1) == 'i') return mb_eregi(substr($pattern, 1, -2), $string); else return mb_ereg(substr($pattern, 1, -1), $string);}}
+if (!function_exists("Gutenberg_PEG_chr_unicode")) {
+    function Gutenberg_PEG_chr_unicode($code) {
+        return html_entity_decode("&#$code;", ENT_QUOTES, "UTF-8");
+    }
+}
+/* Gutenberg_PEG_ord_unicode - get unicode char code from string */
+if (!function_exists("Gutenberg_PEG_ord_unicode")) {
+    function Gutenberg_PEG_ord_unicode($character) {
+        if (strlen($character) === 1) {
+            return ord($character);
+        }
+        $json = json_encode($character);
+        $utf16_1 = hexdec(substr($json, 3, 4));
+        if (substr($json, 7, 2) === "\u") {
+            $utf16_2 = hexdec(substr($json, 9, 4));
+            return 0x10000 + (($utf16_1 & 0x3ff) << 10) + ($utf16_2 & 0x3ff);
+        } else {
+            return $utf16_1;
+        }
+    }
+}
+/* Gutenberg_PEG_peg_char_class_test - simple character class test */
+if (!function_exists("Gutenberg_PEG_peg_char_class_test")) {
+    function Gutenberg_PEG_peg_char_class_test($class, $character) {
+        $code = Gutenberg_PEG_ord_unicode($character);
+        foreach ($class as $range) {
+            if ($code >= $range[0] && $code <= $range[1]) {
+                return true;
+            }
+        }
+        return false;
+    }
+}
 
 /* Syntax error exception */
-if (!class_exists("Gutenberg_PEG_SyntaxError", false)){
-class Gutenberg_PEG_SyntaxError extends Exception
-{
-    public $expected;
-    public $found;
-    public $grammarOffset;
-    public $grammarLine;
-    public $grammarColumn;
-    public $name;
-    public function __construct($message, $expected, $found, $offset, $line, $column)
-    {
-        parent::__construct($message, 0);
-        $this->expected = $expected;
-        $this->found = $found;
-        $this->grammarOffset = $offset;
-        $this->grammarLine = $line;
-        $this->grammarColumn = $column;
-        $this->name = "Gutenberg_PEG_SyntaxError";
+if (!class_exists("Gutenberg_PEG_SyntaxError", false)) {
+    class Gutenberg_PEG_SyntaxError extends Exception {
+        public $expected;
+        public $found;
+        public $grammarOffset;
+        public $grammarLine;
+        public $grammarColumn;
+        public $name;
+        public function __construct($message, $expected, $found, $offset, $line, $column) {
+            parent::__construct($message, 0);
+            $this->expected = $expected;
+            $this->found = $found;
+            $this->grammarOffset = $offset;
+            $this->grammarLine = $line;
+            $this->grammarColumn = $column;
+            $this->name = "Gutenberg_PEG_SyntaxError";
+        }
     }
-};}
+}
 
 class Gutenberg_PEG_Parser {
-
-
     private $peg_currPos          = 0;
     private $peg_reportedPos      = 0;
     private $peg_cachedPos        = 0;
@@ -46,7 +73,7 @@ class Gutenberg_PEG_Parser {
     private $peg_maxFailExpected  = array();
     private $peg_silentFails      = 0;
     private $input                = array();
-
+    private $input_length         = 0;
 
     private function cleanup_state() {
       $this->peg_currPos          = 0;
@@ -62,7 +89,7 @@ private function cleanup_state() {
     }
 
     private function input_substr($start, $length) {
-      if ($length === 1) {
+      if ($length === 1 && $start < $this->input_length) {
         return $this->input[$start];
       }
       $substr = '';
@@ -158,7 +185,7 @@ private function peg_buildException_expectedComparator($a, $b) {
 
     private function peg_buildException($message, $expected, $pos) {
       $posDetails = $this->peg_computePosDetails($pos);
-      $found      = $pos < $this->input_length ? $this->input_substr($pos, 1) : null;
+      $found      = $pos < $this->input_length ? $this->input[$pos] : null;
 
       if ($expected !== null) {
         usort($expected, array($this, "peg_buildException_expectedComparator"));
@@ -327,7 +354,9 @@ private function peg_parseWP_Tag_More() {
         $this->peg_currPos += 4;
       } else {
         $s1 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c1); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c1);
+        }
       }
       if ($s1 !== $this->peg_FAILED) {
         $s2 = array();
@@ -342,7 +371,9 @@ private function peg_parseWP_Tag_More() {
             $this->peg_currPos += 4;
           } else {
             $s3 = $this->peg_FAILED;
-            if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c3); }
+            if ($this->peg_silentFails === 0) {
+                $this->peg_fail($this->peg_c3);
+            }
           }
           if ($s3 !== $this->peg_FAILED) {
             $s4 = $this->peg_currPos;
@@ -375,7 +406,9 @@ private function peg_parseWP_Tag_More() {
                   $this->peg_currPos += 3;
                 } else {
                   $s12 = $this->peg_FAILED;
-                  if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c5); }
+                  if ($this->peg_silentFails === 0) {
+                      $this->peg_fail($this->peg_c5);
+                  }
                 }
                 if ($s12 !== $this->peg_FAILED) {
                   $s11 = array($s11, $s12);
@@ -401,7 +434,9 @@ private function peg_parseWP_Tag_More() {
                   $this->peg_currPos++;
                 } else {
                   $s10 = $this->peg_FAILED;
-                  if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c6); }
+                  if ($this->peg_silentFails === 0) {
+                      $this->peg_fail($this->peg_c6);
+                  }
                 }
                 if ($s10 !== $this->peg_FAILED) {
                   $s9 = array($s9, $s10);
@@ -433,7 +468,9 @@ private function peg_parseWP_Tag_More() {
                       $this->peg_currPos += 3;
                     } else {
                       $s12 = $this->peg_FAILED;
-                      if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c5); }
+                      if ($this->peg_silentFails === 0) {
+                          $this->peg_fail($this->peg_c5);
+                      }
                     }
                     if ($s12 !== $this->peg_FAILED) {
                       $s11 = array($s11, $s12);
@@ -459,7 +496,9 @@ private function peg_parseWP_Tag_More() {
                       $this->peg_currPos++;
                     } else {
                       $s10 = $this->peg_FAILED;
-                      if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c6); }
+                      if ($this->peg_silentFails === 0) {
+                          $this->peg_fail($this->peg_c6);
+                      }
                     }
                     if ($s10 !== $this->peg_FAILED) {
                       $s9 = array($s9, $s10);
@@ -509,7 +548,9 @@ private function peg_parseWP_Tag_More() {
                   $this->peg_currPos += 3;
                 } else {
                   $s6 = $this->peg_FAILED;
-                  if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c5); }
+                  if ($this->peg_silentFails === 0) {
+                      $this->peg_fail($this->peg_c5);
+                  }
                 }
                 if ($s6 !== $this->peg_FAILED) {
                   $s7 = $this->peg_currPos;
@@ -525,7 +566,9 @@ private function peg_parseWP_Tag_More() {
                       $this->peg_currPos += 15;
                     } else {
                       $s9 = $this->peg_FAILED;
-                      if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c8); }
+                      if ($this->peg_silentFails === 0) {
+                          $this->peg_fail($this->peg_c8);
+                      }
                     }
                     if ($s9 !== $this->peg_FAILED) {
                       $s8 = array($s8, $s9);
@@ -585,7 +628,9 @@ private function peg_parseWP_Block_Void() {
         $this->peg_currPos += 4;
       } else {
         $s1 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c1); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c1);
+        }
       }
       if ($s1 !== $this->peg_FAILED) {
         $s2 = array();
@@ -604,7 +649,9 @@ private function peg_parseWP_Block_Void() {
             $this->peg_currPos += 3;
           } else {
             $s3 = $this->peg_FAILED;
-            if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c10); }
+            if ($this->peg_silentFails === 0) {
+                $this->peg_fail($this->peg_c10);
+            }
           }
           if ($s3 !== $this->peg_FAILED) {
             $s4 = $this->peg_parseWP_Block_Name();
@@ -654,7 +701,9 @@ private function peg_parseWP_Block_Void() {
                     $this->peg_currPos += 4;
                   } else {
                     $s7 = $this->peg_FAILED;
-                    if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c12); }
+                    if ($this->peg_silentFails === 0) {
+                        $this->peg_fail($this->peg_c12);
+                    }
                   }
                   if ($s7 !== $this->peg_FAILED) {
                     $this->peg_reportedPos = $s0;
@@ -893,7 +942,9 @@ private function peg_parseWP_Block_Start() {
         $this->peg_currPos += 4;
       } else {
         $s1 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c1); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c1);
+        }
       }
       if ($s1 !== $this->peg_FAILED) {
         $s2 = array();
@@ -912,7 +963,9 @@ private function peg_parseWP_Block_Start() {
             $this->peg_currPos += 3;
           } else {
             $s3 = $this->peg_FAILED;
-            if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c10); }
+            if ($this->peg_silentFails === 0) {
+                $this->peg_fail($this->peg_c10);
+            }
           }
           if ($s3 !== $this->peg_FAILED) {
             $s4 = $this->peg_parseWP_Block_Name();
@@ -962,7 +1015,9 @@ private function peg_parseWP_Block_Start() {
                     $this->peg_currPos += 3;
                   } else {
                     $s7 = $this->peg_FAILED;
-                    if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c5); }
+                    if ($this->peg_silentFails === 0) {
+                        $this->peg_fail($this->peg_c5);
+                    }
                   }
                   if ($s7 !== $this->peg_FAILED) {
                     $this->peg_reportedPos = $s0;
@@ -1008,7 +1063,9 @@ private function peg_parseWP_Block_End() {
         $this->peg_currPos += 4;
       } else {
         $s1 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c1); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c1);
+        }
       }
       if ($s1 !== $this->peg_FAILED) {
         $s2 = array();
@@ -1027,7 +1084,9 @@ private function peg_parseWP_Block_End() {
             $this->peg_currPos += 4;
           } else {
             $s3 = $this->peg_FAILED;
-            if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c14); }
+            if ($this->peg_silentFails === 0) {
+                $this->peg_fail($this->peg_c14);
+            }
           }
           if ($s3 !== $this->peg_FAILED) {
             $s4 = $this->peg_parseWP_Block_Name();
@@ -1048,7 +1107,9 @@ private function peg_parseWP_Block_End() {
                   $this->peg_currPos += 3;
                 } else {
                   $s6 = $this->peg_FAILED;
-                  if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c5); }
+                  if ($this->peg_silentFails === 0) {
+                      $this->peg_fail($this->peg_c5);
+                  }
                 }
                 if ($s6 !== $this->peg_FAILED) {
                   $this->peg_reportedPos = $s0;
@@ -1097,7 +1158,9 @@ private function peg_parseWP_Block_Name() {
             $this->peg_currPos++;
           } else {
             $s5 = $this->peg_FAILED;
-            if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c16); }
+            if ($this->peg_silentFails === 0) {
+                $this->peg_fail($this->peg_c16);
+            }
           }
           if ($s5 !== $this->peg_FAILED) {
             $s6 = $this->peg_parseASCII_AlphaNumeric();
@@ -1123,7 +1186,9 @@ private function peg_parseWP_Block_Name() {
               $this->peg_currPos++;
             } else {
               $s5 = $this->peg_FAILED;
-              if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c16); }
+              if ($this->peg_silentFails === 0) {
+                  $this->peg_fail($this->peg_c16);
+              }
             }
             if ($s5 !== $this->peg_FAILED) {
               $s6 = $this->peg_parseASCII_AlphaNumeric();
@@ -1170,7 +1235,9 @@ private function peg_parseWP_Block_Attributes() {
         $this->peg_currPos++;
       } else {
         $s3 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c18); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c18);
+        }
       }
       if ($s3 !== $this->peg_FAILED) {
         $s4 = array();
@@ -1183,7 +1250,9 @@ private function peg_parseWP_Block_Attributes() {
           $this->peg_currPos++;
         } else {
           $s8 = $this->peg_FAILED;
-          if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c20); }
+          if ($this->peg_silentFails === 0) {
+              $this->peg_fail($this->peg_c20);
+          }
         }
         if ($s8 !== $this->peg_FAILED) {
           $s9 = array();
@@ -1204,7 +1273,9 @@ private function peg_parseWP_Block_Attributes() {
                 $this->peg_currPos++;
               } else {
                 $s11 = $this->peg_FAILED;
-                if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c16); }
+                if ($this->peg_silentFails === 0) {
+                    $this->peg_fail($this->peg_c16);
+                }
               }
               if ($s11 === $this->peg_FAILED) {
                 $s11 = null;
@@ -1215,7 +1286,9 @@ private function peg_parseWP_Block_Attributes() {
                   $this->peg_currPos += 3;
                 } else {
                   $s12 = $this->peg_FAILED;
-                  if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c5); }
+                  if ($this->peg_silentFails === 0) {
+                      $this->peg_fail($this->peg_c5);
+                  }
                 }
                 if ($s12 !== $this->peg_FAILED) {
                   $s8 = array($s8, $s9, $s10, $s11, $s12);
@@ -1253,7 +1326,9 @@ private function peg_parseWP_Block_Attributes() {
             $this->peg_currPos++;
           } else {
             $s7 = $this->peg_FAILED;
-            if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c6); }
+            if ($this->peg_silentFails === 0) {
+                $this->peg_fail($this->peg_c6);
+            }
           }
           if ($s7 !== $this->peg_FAILED) {
             $s6 = array($s6, $s7);
@@ -1277,7 +1352,9 @@ private function peg_parseWP_Block_Attributes() {
             $this->peg_currPos++;
           } else {
             $s8 = $this->peg_FAILED;
-            if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c20); }
+            if ($this->peg_silentFails === 0) {
+                $this->peg_fail($this->peg_c20);
+            }
           }
           if ($s8 !== $this->peg_FAILED) {
             $s9 = array();
@@ -1298,7 +1375,9 @@ private function peg_parseWP_Block_Attributes() {
                   $this->peg_currPos++;
                 } else {
                   $s11 = $this->peg_FAILED;
-                  if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c16); }
+                  if ($this->peg_silentFails === 0) {
+                      $this->peg_fail($this->peg_c16);
+                  }
                 }
                 if ($s11 === $this->peg_FAILED) {
                   $s11 = null;
@@ -1309,7 +1388,9 @@ private function peg_parseWP_Block_Attributes() {
                     $this->peg_currPos += 3;
                   } else {
                     $s12 = $this->peg_FAILED;
-                    if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c5); }
+                    if ($this->peg_silentFails === 0) {
+                        $this->peg_fail($this->peg_c5);
+                    }
                   }
                   if ($s12 !== $this->peg_FAILED) {
                     $s8 = array($s8, $s9, $s10, $s11, $s12);
@@ -1347,7 +1428,9 @@ private function peg_parseWP_Block_Attributes() {
               $this->peg_currPos++;
             } else {
               $s7 = $this->peg_FAILED;
-              if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c6); }
+              if ($this->peg_silentFails === 0) {
+                  $this->peg_fail($this->peg_c6);
+              }
             }
             if ($s7 !== $this->peg_FAILED) {
               $s6 = array($s6, $s7);
@@ -1367,7 +1450,9 @@ private function peg_parseWP_Block_Attributes() {
             $this->peg_currPos++;
           } else {
             $s5 = $this->peg_FAILED;
-            if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c20); }
+            if ($this->peg_silentFails === 0) {
+                $this->peg_fail($this->peg_c20);
+            }
           }
           if ($s5 !== $this->peg_FAILED) {
             $s3 = array($s3, $s4, $s5);
@@ -1413,12 +1498,14 @@ private function peg_parseASCII_AlphaNumeric() {
 
     private function peg_parseASCII_Letter() {
 
-      if (Gutenberg_PEG_peg_regex_test($this->peg_c22, $this->input_substr($this->peg_currPos, 1))) {
+      if (Gutenberg_PEG_peg_char_class_test($this->peg_c22, $this->input_substr($this->peg_currPos, 1))) {
         $s0 = $this->input_substr($this->peg_currPos, 1);
         $this->peg_currPos++;
       } else {
         $s0 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c23); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c23);
+        }
       }
 
       return $s0;
@@ -1426,12 +1513,14 @@ private function peg_parseASCII_Letter() {
 
     private function peg_parseASCII_Digit() {
 
-      if (Gutenberg_PEG_peg_regex_test($this->peg_c24, $this->input_substr($this->peg_currPos, 1))) {
+      if (Gutenberg_PEG_peg_char_class_test($this->peg_c24, $this->input_substr($this->peg_currPos, 1))) {
         $s0 = $this->input_substr($this->peg_currPos, 1);
         $this->peg_currPos++;
       } else {
         $s0 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c25); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c25);
+        }
       }
 
       return $s0;
@@ -1439,12 +1528,14 @@ private function peg_parseASCII_Digit() {
 
     private function peg_parseSpecial_Chars() {
 
-      if (Gutenberg_PEG_peg_regex_test($this->peg_c26, $this->input_substr($this->peg_currPos, 1))) {
+      if (Gutenberg_PEG_peg_char_class_test($this->peg_c26, $this->input_substr($this->peg_currPos, 1))) {
         $s0 = $this->input_substr($this->peg_currPos, 1);
         $this->peg_currPos++;
       } else {
         $s0 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c27); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c27);
+        }
       }
 
       return $s0;
@@ -1452,12 +1543,14 @@ private function peg_parseSpecial_Chars() {
 
     private function peg_parseWS() {
 
-      if (Gutenberg_PEG_peg_regex_test($this->peg_c28, $this->input_substr($this->peg_currPos, 1))) {
+      if (Gutenberg_PEG_peg_char_class_test($this->peg_c28, $this->input_substr($this->peg_currPos, 1))) {
         $s0 = $this->input_substr($this->peg_currPos, 1);
         $this->peg_currPos++;
       } else {
         $s0 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c29); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c29);
+        }
       }
 
       return $s0;
@@ -1465,12 +1558,14 @@ private function peg_parseWS() {
 
     private function peg_parseNewline() {
 
-      if (Gutenberg_PEG_peg_regex_test($this->peg_c30, $this->input_substr($this->peg_currPos, 1))) {
+      if (Gutenberg_PEG_peg_char_class_test($this->peg_c30, $this->input_substr($this->peg_currPos, 1))) {
         $s0 = $this->input_substr($this->peg_currPos, 1);
         $this->peg_currPos++;
       } else {
         $s0 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c31); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c31);
+        }
       }
 
       return $s0;
@@ -1478,12 +1573,14 @@ private function peg_parseNewline() {
 
     private function peg_parse_() {
 
-      if (Gutenberg_PEG_peg_regex_test($this->peg_c32, $this->input_substr($this->peg_currPos, 1))) {
+      if (Gutenberg_PEG_peg_char_class_test($this->peg_c32, $this->input_substr($this->peg_currPos, 1))) {
         $s0 = $this->input_substr($this->peg_currPos, 1);
         $this->peg_currPos++;
       } else {
         $s0 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c33); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c33);
+        }
       }
 
       return $s0;
@@ -1512,7 +1609,9 @@ private function peg_parseAny() {
         $this->peg_currPos++;
       } else {
         $s0 = $this->peg_FAILED;
-        if ($this->peg_silentFails === 0) { $this->peg_fail($this->peg_c6); }
+        if ($this->peg_silentFails === 0) {
+            $this->peg_fail($this->peg_c6);
+        }
       }
 
       return $s0;
@@ -1523,13 +1622,14 @@ public function parse($input) {
     $options = count($arguments) > 1 ? $arguments[1] : array();
     $this->cleanup_state();
 
-    preg_match_all("/./us", $input, $match);
-    $this->input = $match[0];
+    if (is_array($input)) {
+        $this->input = $input;
+    } else {
+        preg_match_all("/./us", $input, $match);
+        $this->input = $match[0];
+    }
     $this->input_length = count($this->input);
 
-    $old_regex_encoding = mb_regex_encoding();
-    mb_regex_encoding("UTF-8");
-
     $this->peg_FAILED = new stdClass;
     $this->peg_c0 = "<!--";
     $this->peg_c1 = array( "type" => "literal", "value" => "<!--", "description" => "\"<!--\"" );
@@ -1553,17 +1653,17 @@ public function parse($input) {
     $this->peg_c19 = "}";
     $this->peg_c20 = array( "type" => "literal", "value" => "}", "description" => "\"}\"" );
     $this->peg_c21 = "";
-    $this->peg_c22 = "/^[a-zA-Z]/";
+    $this->peg_c22 = array(array(97,122), array(65,90));
     $this->peg_c23 = array( "type" => "class", "value" => "[a-zA-Z]", "description" => "[a-zA-Z]" );
-    $this->peg_c24 = "/^[0-9]/";
+    $this->peg_c24 = array(array(48,57));
     $this->peg_c25 = array( "type" => "class", "value" => "[0-9]", "description" => "[0-9]" );
-    $this->peg_c26 = "/^[-_]/";
+    $this->peg_c26 = array(array(45,45), array(95,95));
     $this->peg_c27 = array( "type" => "class", "value" => "[-_]", "description" => "[-_]" );
-    $this->peg_c28 = "/^[ \\t\\r\\n]/";
+    $this->peg_c28 = array(array(32,32), array(9,9), array(13,13), array(10,10));
     $this->peg_c29 = array( "type" => "class", "value" => "[ \t\r\n]", "description" => "[ \t\r\n]" );
-    $this->peg_c30 = "/^[\\r\\n]/";
+    $this->peg_c30 = array(array(13,13), array(10,10));
     $this->peg_c31 = array( "type" => "class", "value" => "[\r\n]", "description" => "[\r\n]" );
-    $this->peg_c32 = "/^[ \\t]/";
+    $this->peg_c32 = array(array(32,32), array(9,9));
     $this->peg_c33 = array( "type" => "class", "value" => "[ \t]", "description" => "[ \t]" );
 
     $peg_startRuleFunctions = array( 'Document' => array($this, "peg_parseDocument") );
@@ -1585,7 +1685,6 @@ public function parse($input) {
 
     $peg_result = call_user_func($peg_startRuleFunction);
 
-    mb_regex_encoding($old_regex_encoding);
     if ($peg_result !== $this->peg_FAILED && $this->peg_currPos === $this->input_length) {
       $this->cleanup_state(); // Free up memory
       return $peg_result;
diff --git a/package.json b/package.json
index efbac118e9c539..6137802c3b1452 100644
--- a/package.json
+++ b/package.json
@@ -65,7 +65,7 @@
     "node-sass": "^4.5.0",
     "pegjs": "^0.10.0",
     "pegjs-loader": "^0.5.1",
-    "phpegjs": "1.0.0-beta5",
+    "phpegjs": "1.0.0-beta7",
     "postcss-loader": "^1.3.3",
     "prismjs": "^1.6.0",
     "raw-loader": "^0.5.1",
diff --git a/phpunit/class-dynamic-blocks-render-test.php b/phpunit/class-dynamic-blocks-render-test.php
index 893353831b75a0..62730c44a93ea6 100644
--- a/phpunit/class-dynamic-blocks-render-test.php
+++ b/phpunit/class-dynamic-blocks-render-test.php
@@ -44,12 +44,6 @@ function tearDown() {
 	 * @covers do_blocks
 	 */
 	function test_dynamic_block_rendering() {
-		if ( ! extension_loaded( 'mbstring' ) ) {
-			$this->markTestSkipped(
-				'The mbstring PHP extension is not installed.'
-			);
-		}
-
 		$settings = array(
 			'render' => array(
 				$this,
@@ -86,12 +80,6 @@ function test_dynamic_block_rendering() {
 	 * @covers do_blocks
 	 */
 	function test_dynamic_block_rendering_with_content() {
-		if ( ! extension_loaded( 'mbstring' ) ) {
-			$this->markTestSkipped(
-				'The mbstring PHP extension is not installed.'
-			);
-		}
-
 		$settings = array(
 			'render' => array(
 				$this,
diff --git a/phpunit/class-parsing-test.php b/phpunit/class-parsing-test.php
index 84e2bdde203aae..176914fa919386 100644
--- a/phpunit/class-parsing-test.php
+++ b/phpunit/class-parsing-test.php
@@ -42,12 +42,6 @@ function pass_parser_fixture_filenames( $filename ) {
 	 * @dataProvider parsing_test_filenames
 	 */
 	function test_parser_output( $html_filename, $parsed_json_filename ) {
-		if ( ! extension_loaded( 'mbstring' ) ) {
-			$this->markTestSkipped(
-				'The mbstring PHP extension is not installed.'
-			);
-		}
-
 		$html_path        = self::$fixtures_dir . '/' . $html_filename;
 		$parsed_json_path = self::$fixtures_dir . '/' . $parsed_json_filename;
 
@@ -60,8 +54,7 @@ function test_parser_output( $html_filename, $parsed_json_filename ) {
 		$html            = file_get_contents( $html_path );
 		$expected_parsed = json_decode( file_get_contents( $parsed_json_path ), true );
 
-		$parser = new Gutenberg_PEG_Parser;
-		$result = $parser->parse( $html );
+		$result = gutenberg_parse_blocks( $html );
 
 		$this->assertEquals(
 			$expected_parsed,
diff --git a/phpunit/class-performance-test.php b/phpunit/class-performance-test.php
index 6a7e5a6fcdca81..56df5b79db99b2 100644
--- a/phpunit/class-performance-test.php
+++ b/phpunit/class-performance-test.php
@@ -13,12 +13,11 @@ function test_parse_large_post() {
 			$html = file_get_contents(
 				dirname( __FILE__ ) . '/fixtures/long-content.html'
 			);
-			$parser = new Gutenberg_PEG_Parser;
 
 			$start = microtime( true );
 			$start_mem = memory_get_usage();
 
-			$parser->parse( $html );
+			$blocks = gutenberg_parse_blocks( $html );
 
 			$time = microtime( true ) - $start;
 			$mem = memory_get_usage() - $start_mem;