$re = '/(?s)```.*?```|`[^`]*`/ms';
$str = 'some text here
some more
``` some code block
with markdown
```
some `inline code` too
and more code blocks:
``` xojo
This must have three backticks
flanking it
```
this text isn\'t matched...';
$subst = "\n----\n";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php