adding rel="nofollow" while saving data

Question

I have my application to allow users to write comments on my website. Its working fine. I also have tool to insert their weblinks in it. I feel good with contents with their own weblinks.

Now i want to add rel="nofollow" to every links on content that they have been written.

I would like to add rel="nofollow" using php i.e while saving data.

So what's a simple method to add rel="nofollow" or updated rel="someother" with rel="someother nofollow" using php

a nice example will be much efficient

Answer 1

Regexs really aren't the best tool for dealing with HTML, especially when PHP has a pretty good HTML parser built in.

This code will handle adding nofollow if the rel attribute is already populated.

$dom = new DOMDocument;

$dom->loadHTML($str);

$anchors = $dom->getElementsByTagName('a');

foreach($anchors as $anchor) { 
    $rel = array(); 

    if ($anchor->hasAttribute('rel') AND ($relAtt = $anchor->getAttribute('rel')) !== '') {
       $rel = preg_split('/\s+/', trim($relAtt));
    }

    if (in_array('nofollow', $rel)) {
      continue;
    }

    $rel[] = 'nofollow';
    $anchor->setAttribute('rel', implode(' ', $rel));
}

var_dump($dom->saveHTML());

CodePad.

The resulting HTML is in $dom->saveHTML(). Except it will wrap it with html, body elements, etc, so use this to extract just the HTML you entered...

$html = '';

foreach($dom->getElementsByTagName('body')->item(0)->childNodes as $element) {
    $html .= $dom->saveXML($element, LIBXML_NOEMPTYTAG);
}

echo $html;

If you have >= PHP 5.3, replace saveXML() with saveHTML() and drop the second argument.

Example

This HTML...

<a href="">hello</a>

<a href="" rel="">hello</a>

<a href="" rel="hello there">hello</a>

<a href="" rel="nofollow">hello</a>

...is converted into...

<a href="" rel="nofollow">hello</a>

<a href="" rel="nofollow">hello</a>

<a href="" rel="hello there nofollow">hello</a>

<a href="" rel="nofollow">hello</a>

Answer 2

Good Alex. If it is in the form of a function it is more useful. So I made it below:

function add_no_follow($str){ 
  $dom = new DOMDocument;

  $dom->loadHTML($str);

  $anchors = $dom->getElementsByTagName('a');

  foreach($anchors as $anchor) { 
      $rel = array(); 

      if ($anchor->hasAttribute('rel') AND ($relAtt = $anchor->getAttribute('rel')) !== '') {
         $rel = preg_split('/\s+/', trim($relAtt));
      }

      if (in_array('nofollow', $rel)) {
        continue;
      }

      $rel[] = 'nofollow';
      $anchor->setAttribute('rel', implode(' ', $rel));
  }

  $dom->saveHTML();

  $html = '';

  foreach($dom->getElementsByTagName('body')->item(0)->childNodes as $element) {
      $html .= $dom->saveXML($element, LIBXML_NOEMPTYTAG);
  }

  return $html;      
}

Use as follows :

  $str = "Some content with link Some content  ... ";

 $str = add_no_follow($str);