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));
        }
    }


    $replacementText = ' <a href="machinery-safety">machinery safety</a>';

    $subStr = substr($output, $rStart, $rLength);
    $rSubStr = $subStr ;
      
    if (strpos($subStr, $replacementText ) === false)
      $rSubStr = str_replace_once(' machinery safety', $replacementText, $subStr);    
      
      
    $modx->documentOutput = str_replace($subStr, $rSubStr, $output);
}
?>​

 </div> <!-- Keyword Replacement Start -->
    <div id="center">

<?php
//$output = str_replace(' machinery safety', ' <b>machinery safety</b>', $modx->documentOutput);
  //$modx->documentOutput = $output;  

$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,European Directive,CE Marking"; \\ ensure no spaces in before and after comma. Seperate keywords by commas
    $array = explode(",", $keywords);
    
    print_r($array);
      
    foreach ($array as &$value) {
      
      $replacementText = ' <a href="'.$value.'">'.$value.'</a>'; // might need to replace spaces with something for the href bit.
      
      if (strpos($rSubStr, $replacementText ) === false)
         $rSubStr = str_replace_once(' '.$value, $replacementText, $rSubStr);          
      
    }
      
    $modx->documentOutput = str_replace($subStr, $rSubStr, $output);
      //$modx->documentOutput = $tv;
}
?>​