Syntax Highlighting variables not appearing

Can anyone explain why this is happening. I am using the following code For giving code examples on my website with syntax highlighting $text = '&lt;?php \$my_code = "echo 'text text text text'; \$foo = 'bar';"; example_function(\$my_code); ?&gt'; $body = preg_replace('/&lt;(.*?)&gt;/es', 'highlight_string("<\\1>", true)', $text); echo $body; //Returns: <?php = 'echo \'text text text text\'\'; = \'bar\'; highlight_string(, true); ?> //I want: <?php $my_code = "echo 'text text text text'; $foo = 'bar';"; example_function($my_code); ?>