Erreur de connexion a la base de donnée

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<b>Fatal error</b>:  Uncaught Error: Call to a member function prepare() on null in /homepages/25/d851002376/htdocs/uplife/site/index.php:34
Stack trace:
#0 {main}
  thrown in <b>/homepages/25/d851002376/htdocs/uplife/site/index.php</b> on line <b>34</b><br />