Warning: mysqli::__construct(): Headers and client library minor version mismatch. Headers:50560 Library:50640 in /var/www/web618/html/diehitte/config.php on line 8

<form method="post" action="index.php?show=members">
<table style="width:90%" border="0" cellspacing="1" cellpadding="0" class="forum">
<tr><td colspan="2" class="headb">Members</td></tr><tr><td class="rightc">
<select class="form" id="look" name="look">
<option value="">Ansicht</option>
<option value="">----</option>
<option value="list" >Liste</option>
<option value="tree" >Baum</option>
</select> 
<select class="form" id="squad" name="squad">
<option value="">Alle Hittenmember</option>
<option value="">----</option>

Fatal error: Uncaught Error: Call to undefined function mysql_query() in /var/www/web618/html/diehitte/show/members.php:24
Stack trace:
#0 /var/www/web618/html/diehitte/index.php(44): include()
#1 {main}
  thrown in /var/www/web618/html/diehitte/show/members.php on line 24