function highlight($word, $subject) { 
    
    $split_subject = explode(" ", $subject); 
    $split_word = explode(" ", $word); 

    foreach ($split_subject as $k => $v){ 
           foreach ($split_word as $k2 => $v2){ 
               if($v2 == $v){ 
                   
                   $split_subject[$k] = "<span class='highlight'>".$v."</span>"; 
               
               } 
           } 
      } 
      
      return implode(' ', $split_subject); 
}

Highlight Search Words

PHP