str_replace() not replacing with <strong> element - php

Question

I want to be able to create a link as follows, when a user starts typing in a search field. Let's say he types the letter a:
#<strong>a</strong>rig<strong>a</strong>to
PHP:
// sets up database conection to variable $dbh
require_once '../includes/bootstrap.php';
if ($_SERVER['REQUEST_METHOD'] == 'GET') {
$tag = (!empty($_GET['tag'])) ? "%$_GET[tag]%" : false ;
if ($tag) {
$stmt = $dbh->prepare('SELECT `tag` FROM `tags` WHERE `tag` LIKE ?');
$result = array();
$stmt->bindParam(1, $tag, PDO::PARAM_STR);
$stmt->execute();
// store result
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
$result[] = $row['tag'];
}
$tags = '';
// create links for results
foreach ($result as $value) {
$row = "<li><a href='http://google.com'>" . str_replace($tag, '<strong>' . $tag . '</strong>', $value) . '</a></li>';
$tags .= $row;
}
echo $tags;
}
}
Result of $tags when user types in the letter a:
<li>#arigato</li>
<li>#arizona</li>
<li>#cantalupi</li>
<li>#clearwater</li>
<li>#florida</li>
<li>#happy</li>
<li>#mamadas</li>
<li>#miriam</li>
<li>#nissan</li>
<li>#sauce</li>
<li>#sentra</li>
<li>#usa</li>
<li>#vegas</li>
<li>#was</li>
<li>#watches</li>
For some reason it is not putting in the <strong> tag as desired.

Answer 1

I think this is happening because of this line:
$tag = (!empty($_GET['tag'])) ? "%$_GET[tag]%" : false ;
This variable is used for the MySQL statement, however later on it is also used for the str_replace(), the problem is that it is trying to find %$_GET[tag]% for replacement, not the value in the $_GET variable.
Try this code instead:
// sets up database conection to variable $dbh
require_once '../includes/bootstrap.php';
if ($_SERVER['REQUEST_METHOD'] == 'GET') {
$tagStr = $_GET['tag'];
$tag = (!empty($_GET['tag'])) ? "%$_GET[tag]%" : false ;
if ($tag) {
$stmt = $dbh->prepare('SELECT `tag` FROM `tags` WHERE `tag` LIKE ?');
$result = array();
$stmt->bindParam(1, $tag, PDO::PARAM_STR);
$stmt->execute();
// store result
while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
$result[] = $row['tag'];
}
$tags = '';
// create links for results
foreach ($result as $value) {
$row = "<li><a href='http://google.com'>" . str_replace($tagStr, '<strong>' . $tagStr . '</strong>', $value) . '</a></li>';
$tags .= $row;
}
echo $tags;
}
}