Connection error: SQLSTATE[HY000] [1049] Unknown database 'billing_system'<br />
<b>Warning</b>:  Undefined array key "role" in <b>C:\xampp\htdocs\billing\backend\api\contracts.php</b> on line <b>13</b><br />
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<b>Warning</b>:  Undefined array key "user_id" in <b>C:\xampp\htdocs\billing\backend\api\contracts.php</b> on line <b>16</b><br />
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<b>Fatal error</b>:  Uncaught Error: Call to a member function prepare() on null in C:\xampp\htdocs\billing\backend\models\Contract.php:59
Stack trace:
#0 C:\xampp\htdocs\billing\backend\api\contracts.php(17): Contract-&gt;readByClient()
#1 {main}
  thrown in <b>C:\xampp\htdocs\billing\backend\models\Contract.php</b> on line <b>59</b><br />