The highlight_string() function outputs a syntax highlighted version of str using the colors defined in the built-in syntax highlighter for PHP.
If the second parameter return is set to TRUE then highlight_string() will return the highlighted code as a string instead of printing it out. If the second parameter is not set to TRUE then highlight_string() will return TRUE on success, FALSE on failure.
Note: The return parameter became available in PHP 4.2.0. Before this time it behaved like the default, which is FALSE
See also highlight_file().