Highligh key words in PHP search result - php

Question

I have the below code and i am trying to highlight the search keywords on echoing the results. I have tried what is here
and here
but didn't work.
Please where am i getting it wrong.
Below is my code
if (isset($_GET["mainSearch"]))
{
$condition = '';
// $mainSearch = SQLite3::escapeString($_GET['mainSearch']);
$keyword = $_GET['mainSearch'];
$query = explode(" ", $keyword);
foreach ($query as $text)
{
$condition .= "question LIKE '%".SQLite3::escapeString($text)."%' OR ";
}
$condition = substr($condition, 0, -4);
$order = " ORDER BY quiz_id DESC ";
$sql_query = "SELECT * FROM questions WHERE " . $condition . ' '. $order;
$sql_query_count = "SELECT COUNT(*) as count FROM questions WHERE " . $condition .' '. $order;
$result = $db->query($sql_query);
$resultCount = $db->querySingle($sql_query_count);
if ($resultCount > 0)
{
if ($result)
{
while ($row = $result->fetchArray(SQLITE3_ASSOC))
{
//TRYING TO HIGHLIGHT SEARCH KEYWORD HERE.
$wording = str_replace($keyword, "<span style='font-weight: bold;'>".$keyword."</span>", $row['answer']);
echo '<div class="quesbox_3">
<div class="questitle">
<h2>'.$row["question"].'</h2>
</div>
<div class="quesanswer">'.$wording.'</div>
</div>';
}
}
}
else
{
echo "No results found";
}
}
Thank you very much.