Try...
Simple way to create csv file.
<?php 
mysql_connect('hostname', 'username', 'password');
mysql_select_db('dbname');
$qry = mysql_query("SELECT * FROM tablename");
$data = "";
while($row = mysql_fetch_array($qry)) {
  $data .= $row['field1'].",".$row['field2'].",".$row['field3'].",".$row['field4']."\n";
}
$file = 'file.csv';
chmod($file, 0777);
file_put_contents($file, $data);
?>

Try...

Simple way to create csv file.

<?php 
mysql_connect('hostname', 'username', 'password');
mysql_select_db('dbname');
$qry = mysql_query("SELECT * FROM tablename");
$data = "";
while($row = mysql_fetch_array($qry)) {
  $data .= $row['field1'].",".$row['field2'].",".$row['field3'].",".$row['field4']."\n";
}
$file = 'file.csv';
chmod($file, 0777);
file_put_contents($file, $data);
?>