Conditional str_replace for pagination

H everyone,

I have the following:

$html = '<ul class="pagination-all">';
     $html .= '<li class="pagination-start"><div class="img-start"></div>'.$list['start']['data'].'</li>';
     $html .= '<li class="pagination-prev"><div class="img-prev"></div>'.$list['previous']['data'].'</li>';
     $html .= '<ul class="pagination-data">';
     foreach($list['pages'] as $page) {
         $html .= '<li>'.$page['data'].'</li>';
     }
     $html .= '</ul>';
     $html .= '<li class="pagination-next">'. $list['next']['data'].'<div class="img-next"></div></li>';
     $html .= '<li class="pagination-end">'. $list['end']['data'].'<div class="img-end"></div></li>';
     $html .= '</ul>';
 
     return $html;
 

I was wondering how to make it so if it finds Start , string replaces "img-start" to "img-start-active". If it finds span class="pagenav"> End , string replaces "img-end" to "img-end-active".

I attempted:

$string = $html;
 if(strstr($string, '<span class="pagenav"> Start </span>'))
 {
 echo str_replace("img-start", "img-start-active", $string);
 }
 else
 {
 echo " ";
 }
 

Unfortunately, I don't believe I used this properly. What ended up was - while I got the desired string replacement given the condition, it echoed the whole pagination but without the formatting.

This is the image:

So it was a mess.

Is there a way to do this search and replace but without creating a second "pagination"?

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