PHP Cookbook

11.9. Converting ASCII to HTML

Problem

You want to turn plaintext into reasonably formatted HTML.

Solution

First, encode entities with htmlentities( ) ; then, transform the text into various HTML structures. The pc_ascii2html( ) function shown in Example 11-3 has basic transformations for links and paragraph breaks.

Example 11-3. pc_ascii2html( )

function pc_ascii2html($s) {
  $s = htmlentities($s);
  $grafs = split("\n\n",$s);
  for ($i = 0, $j = count($grafs); $i < $j; $i++) {
    // Link to what seem to be http or ftp URLs
    $grafs[$i] = preg_replace('/((ht|f)tp:\/\/[^\s&]+)/',
                              '<a href="$1">$1</a>',$grafs[$i]);

    // Link to email addresses
    $grafs[$i] = preg_replace('/[^@\s]+@([-a-z0-9]+\.)+[a-z]{2,}/i',
        '<a href="mailto:$1">$1</a>',$grafs[$i]);

    // Begin with a new paragraph 
    $grafs[$i] = '<p>'.$grafs[$i].'</p>';
  }
  return join("\n\n",$grafs);
}

Discussion

The more you know about what the ASCII text looks like, the better your HTML conversion can be. For example, if emphasis is indicated with *asterisks* or /slashes/ around words, you can add rules that take care of that, as follows:

$grafs[$i] = preg_replace('/(\A|\s)\*([^*]+)\*(\s|\z)/',
                          '$1<b>$2</b>$3',$grafs[$i]);
$grafs[$i] = preg_replace('{(\A|\s)/([^/]+)/(\s|\z)}',
                          '$1<i>$2</i>$3',$grafs[$i]);

See Also

Documentation on preg_replace( ) at http://www.php.net/preg-replace.