title: PHP replace data only in one column of csv
body: <p>I need to replace the values only from the third column in my csv. And no where else.
  Column 3 of my csv contains only a 'J' or a'N' and i need to change them to '5' or '0'. But right now i it changes always all found N's and J#s in the whole file. But i need it only updated in the third column. </p>
  
  <p>I use the following code to open and rewrite my csv. But it writes always all found Letters to 5 or 0.</p>
  
  <pre><code>$csvfile = 'csvfile.csv';
  if (file_exists($csvfile)) {
          unlink($csvfile);
      echo "Alte $csvfile entfernt!";
  } else {
      echo "Keine alte $csvfile vorhanden";
  }
  
  $row = 0;
  $fp = fopen('csvfile.csv', 'w');
  if (($handle = fopen("oldCSV.csv", "r")) !== FALSE) {
      while (($data = fgetcsv($handle, 200000, ",")) !== FALSE) {
      $num = count($data);
      $dataold = ['J', 'N'];                                                            
      $datanew = ['5', '0'];
      echo "&lt;p&gt; $num Felder in Zeile $row: &lt;br /&gt;&lt;/p&gt;\n";
      $row++;
      for ($c=0; $c &lt; $num; $c++) {
          fputs($fp, str_replace($dataold, $datanew, $data[$c] . "\n"));
      }
    }
  }
  
  fclose($fp);
  </code></pre>