Internal Linking Plugin For Modx

<?php
$output = $modx->documentOutput;
  
$rStart = strpos($output, '<!-- Keyword Replacement Start -->');
$rStop =  strpos($output, '<!-- Keyword Replacement End -->');

$rLength = $rStop - $rStart;  
  
if (($rStop !== false) && ($rStart !== false))
{   
    if (!function_exists('str_replace_once')) {
        function str_replace_once($needle , $replace , $haystack){
            // Looks for the first occurence of $needle in $haystack
            // and replaces it with $replace.
            $pos = strpos($haystack, $needle);
            if ($pos === false) {
                // Nothing found
                return $haystack;
            }
            return substr_replace($haystack, $replace, $pos, strlen($needle));
        }
    }
    
    $subStr = substr($output, $rStart, $rLength);
    $rSubStr = $subStr ;
      
      //$keywords = "machinery safety|machinery-safety.html,European Directive|european-directives.html,CE Marking|ce-marking.html"; // move whats in the speech marks to a template variable called relinklist
    $keywords = $modx->getTemplateVarOutput(array("relinklist"));  
    $array = explode(",", $keywords['relinklist'] );  
    
      
    foreach ($array as &$value) {
      
      $myValues = explode("|", $value);     
      $replacementText = ' <a href="'.$myValues[1].'">'.$myValues[0].'</a> ';
      
      if (strpos($rSubStr, $replacementText ) === false)
         $rSubStr = str_replace_once(' '.$myValues[0].' ', $replacementText, $rSubStr);          
    }
      
    $modx->documentOutput = str_replace($subStr, $rSubStr, $output);
}
?>​

    $keywords = "keyword1|http://www.example.co.uk,keyword2|http://www.example.co.uk/keyword2";
    $array = explode(",", $keywords );

$output = &$modx->documentOutput;