title: how to fix Undefined offset: 1
body: <p>i am not familiar with this kind of error <code>Undefined error offset: 1</code>. how im i going to fix this error?</p>
  
  <p>here is my code together with my query:</p>
  
  <pre><code>SELECT document_crew_id,doc_number,full_name,id,doc_type,date_issue,date_expiry,place_of_issue,crew_status, 
  GROUP_CONCAT(doc_number) as document_number, 
  GROUP_CONCAT(date_issue) as date_issued, 
  GROUP_CONCAT(date_expiry) as date_expired, 
  GROUP_CONCAT(place_of_issue) as place_issueda 
  from crew_documents_table join info 
  on crew_documents_table.document_crew_id = info.id where doc_type = '1' or doc_type = '2' and crew_status = 'LINEUP PENDING' group by full_name
  
          $value = $row1['document_number'];
          $value = explode(",", $value);
          $doc_numn2 = $value[1];
  </code></pre>
  
  <p>thank you in advance</p>