如何使用PHP增加MSSQL表列中的字符数

Currently, I have a table column that has a text limit of 255 (Varchar[255]), I would like the number of characters increased to 4000 or more. What would the code be, if ran through a PHP page, to make this modification?

Note* - I have modified a column with a varchar(100) to varchar(255), it seems that my columns cannot exceed a varchar of 255.

So far I have used this - alas, it doesn't work:

<?php
$dbhost = 's036';
$dbuser = 'rost';
$dbpass = 'rosword';
 $conn=mssql_connect('smtscom','sTrsr','Rsa');
mssql_select_db('Gsa',$conn);
if(! $conn )
{
  die('Could not connect: ' . mssql_get_last_message());
}
echo 'Connected successfully';
$sql = "ALTER TABLE new_tders2 ALTER 

COLUMN description varchar(4000)";

mssql_select_db('Gsa');
$retval = mssql_query( $sql, $conn );
if(! $retval )
{
  die('Could not create table:');
}
echo "Table column modified successfully
";
mssql_close($conn);
?>

When I run the PHP page (the code above), it says "Table column modified successfully", but I still can only input 255 characters into the column.

I figured it out - instead of using VARCHAR(4000), use TEXT. It will exceed 4000 characters, and allow up to 64 Kb, 2 bytes overhead. However, this is fine in my case, as more than 4000 characters is fine for this part of the website.

Here is the new (working) code:

<?php
$dbhost = 's036';
$dbuser = 'rost';
$dbpass = 'rosword';
 $conn=mssql_connect('smtscom','sTrsr','Rsa');
mssql_select_db('Gsa',$conn);
if(! $conn )
{
  die('Could not connect: ' . mssql_get_last_message());
}
echo 'Connected successfully';
$sql = "ALTER TABLE new_tders2 ALTER 

COLUMN description TEXT";

mssql_select_db('Gsa');
$retval = mssql_query( $sql, $conn );
if(! $retval )
{
  die('Could not create table:');
}
echo "Table column modified successfully
";
mssql_close($conn);
?>

Thank you to all those that tried to answer.