PHP搜索大小写字母

是否有一种方法可以让PHP搜索并返回结果，无论大小写字母的差异。我目前的代码搜索，只返回与大写和小写的确切结果。所以我把它全部小写，但我希望结果有正确的大写字母的名字。

通过LDAP进行搜索。值是来自活动目录的信息，搜索正在搜索人名，并给出该人的电话号码等结果

// Address Book Search
$search .= "<div class='border'>'n";
$search .= "<h1>Search for Staff</h1>";
$search .= '<form class="search-form-wrapper" method="GET">
                <input type="text" name="q" id="search" placeholder="Search for Staff..." required>
                <input type="submit" value="go" id="submit">
            </form><br><br>';
if (count($staff)) {
    if (isset($_GET['q'])) {
        $query = strip_tags($_GET['q']);
        $query = str_replace('%27', "'", $query);
        $query = strtolower($query);
        $search .= "<table class='address_book'><tr><th>Name</th><th>Title</th><th>Phone</th><th>Mobile</th><th>Email</th><th>Dept</th></tr>'n";
        foreach ($staff as $key => $details) {
            $details['displayname'] = strtolower($details['displayname']);
            if(substr_count($details['displayname'], $query)){
            $search .= "<tr><td>{$details['displayname']}</td>'n";
            $search .= "<td>{$details['title']}</td>'n";
            $search .= "<td>{$details['telephonenumber']}</td>'n";
            $search .= "<td>{$details['mobile']}</td>'n";
            $search .= "<td><a href='mailto:{$details['mail']}'>{$details['mail']}</a></td>'n";
            $search .= "<td>{$details['department']}</td>'n";
            $search .= "</tr>'n";
            }
        }
        $search .= "</table>'n";
    }
}
$search .= "</div><br>";