Optimizing code parsing function

[PaulRyan]

I have created a function to parse code blocks within my blog posts, it took me a little while to get my head around a few things, but I've completed it nonetheless.

I would like to know if anyone can spot and functions I should be using, or ways of shortening the code down (without making things to complicated) or if anyone has a better function to do the same job.

 

PLEASE NOTE!! I had to add backslashes the my own code blocks within my $blogPost so I could post it on here without breaking the code parser.
 

<style>
  .codeBlock{
    background: #FAFAFA;
    padding: 3px 5px;
    border: 1px solid #CCC;
    margin-top: 15px;
  }
 
  .lineNumber{
    color: #444;
  }
</style>

<?PHP

  //### Example blog post content
  $blogPost  = 'Testing my PHP code display/heightlighting parsing function.' .PHP_EOL;
  $blogPost .= '4cb09423dfa8b96afcf98c9361927b7a'), '', htmlentities($blogPost));  
 
    //### Iterate over all code blocks and replace markers with code block
    foreach($matches[1] AS $key => $codeBlock) {
    
      //### Highlight code string
      $codeBlock = highlight_string($codeBlock, TRUE);
      //### Remove the line endings from top and bottom of code block
      $codeBlock = preg_replace('#'.PHP_EOL.'#', '', $codeBlock);
      
      //### Explode the lines, so we can add line numbers
      $codeLines = explode('<br />', $codeBlock);
      //### Start output with code tag, to fix first line number error (shows as plain text)
      $codeBlockLines = '<code>';
      
      //### Iterate over the code lines and add the line number with the line of code
      foreach($codeLines AS $line => $code) {
        $codeBlockLines .= '<span class="lineNumber">'. $line. ' |</span> '.$code . PHP_EOL;
      }      
      
      //### Finally replace the code block back into the blog post
      $blogPost = str_replace('[?CODEBLOCK '.$key.'?]', '<div class="codeBlock">'. $codeBlockLines .'</div>', $blogPost);
    }
    
    //### Create new lines with output
    return nl2br($blogPost);
  }
 
  echo blog_post_parse($blogPost);

?>