PHP string concatination

Hello,

basically what I am trying to do is to create a basic wizard for creating a query in PHP, interfacing with a MYSQL database. I can work all that. however I am having a problem with concatinating a string properly. my code is as follows:

<?php $tableselection = $_POST["table"];

include ("connection.php");




/*variables used:
$tableselection - tablename
$collum_selections[] - collum selections
$number_menus - number of collums in a table
*/

echo"Table selected:     $tableselection<br/>";

?>





<FORM method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
<?

/////////////////////////// select columns///////////////////////////


$con = mysql_connect($server,$username,$password);

mysql_select_db($databasename, $con);



$result = mysql_query("SHOW COLUMNS FROM SystemUsers");

//$result = mysql_query("SHOW COLUMNS FROM $tableselection");

$number_fields=mysql_num_rows($result);

//echo "<input type='hidden' name='filtercol_". $i ."' value='". $row[0] ."' />";

echo "<input type='hidden' 'text' name='number_fields' value='$number_fields' />";

$i=0;
while($row = mysql_fetch_array($result, MYSQL_NUM))


{
//    echo "Collum selected :        {$row[0]}";


//echo "Complete sum of fields is:   $number_fields";

//<SELECT name=field_function.$i>
echo"
<SELECT name=field_function[]>
<OPTION value=''>please select</OPTION>
<OPTION value='{$row[0]}, '>None</OPTION>
<OPTION value='AVG({$row[0]}), '>Average</OPTION>
<OPTION value='sum( {$row[0]}) as Total {$row[0]}'>Sum</OPTION>
<OPTION value='COUNT({$row[0]}), '>Count</OPTION>
<OPTION value='$i'>$i</OPTION>
</SELECT>
<br/><INPUT TYPE = 'Text' NAME = 'field_filter[]'><br/>";

$i++;

}

mysql_close($con);

//echo "<input type=Submit value=enter>";

?>
<input type="submit" />
</form>



<?

// passes variables from the above form
$field1 = $_POST['number_fields'];
echo "Number of rows          $field1<br/>";

$field2 = $_POST['field_function'];

$field3 = $_POST['field_filter'];

//counts the number of elements in array
$extra1 = count($field3);

echo "<br/>the number of extra string sectons needed is:  $extra1  <br/>";


$G = 0;
while ($G <= $field1) {
//outputs the results
echo $field2[$G];
echo "<br/>";
// creates the string main sql string
$querystring2 = $querystring2. $field2[$G];
$G++;  
}

//foreach( $field3 as $key => $value){
//      echo "i bet this dont bleedin work <br />";
//}

$H = 0;
while ($H <= $field1){
echo "<br/>";
echo $field3[$H];
// creates the extra sql string
//$querystring3 = $querystring3.$field3[$H]." AND ";
$querystring3 = $querystring3.$field3[$H];
$H++;  
}
echo "extra string here is: $querystring3";

?>

there seems to be 2 problems.
1, for some reason my code will not count the number of values in an array. the array comes from a textbox,  field_filter[] .

basically what I am trying to do is to provide a facility for the user to select a collum and if required add a value to be passed into a MYsql SELECT........ From..........where statement.


2, it adds multiple " AND " to the end of the string

the code for problem 2 is:
//$querystring3 = $querystring3.$field3[$H]." AND ";
$querystring3 = $querystring3.$field3[$H];

if I use the one that is commmented out then it will add multiple 'AND' on the end of the string, but if I miss out the .AND on the end, it adds the requisite number of values.



here is a URL for what I have working so far!
http://www.gavinbuczko.co.uk/phpreportmakerstage2.php

I am sure it is something silly, but I cant see what.

thanks,

Gavin