Well, I found two solutions.
1) I use ADO to connect to MSSQL. ADO is more slower (up to 2 times!), than mssql_* functions, but there are no connection problems
2) I set connection timeout in code:
function getmt()
{
   list($usec, $sec)=explode(" ",microtime());
   return ((float)$usec+(float)$sec);
}
$time_st=getmt();
$db=new CSql;
while(!$db->connect_db($Host, $Name, $Login, $Passw))
   if(round(getmt()-$time_st, 0)>60) break;
if(!$db->dbc) die("Connection failed!"); 

It is too hard to use odbc_* functions, because there are a lot of bugs with TEXT field type ? I must put it on the last position in query and use CONVERT(varbinary, other way I get ODBC errors.

I hope that mssql_* and odbc_* problems will be solved in future PHP releases.

I think that this problem occurs due to usage of old DB-Lib for connecting to MSSQL. There are another bug ? that you can?t fetch varchar more than 256-character length (you have to convert it to TEXT).
It?s a pity, but the best way to work with MSSQL now is using ADO (no connection/long varchar/Unicode problems).

I am running three Windows XP SP2 boxes as developer workstations, all PHP 5.2.5, installed into c:\php to avoid the space in "Program Files", and the MS Sql connection works perfectly on one of the machines, but not the other two. All three boxes are on the same LAN, can connect to the database using MS SQL Studio, and all have IIS 5.1. I have copied the PHP installation from the working PC to the others, no difference. This is whether the connection is to a remote or local SQL server.

Have you try editing php.ini mssql.max_procs?
mssql.max_procs = -1

Hi, same problem detected here (connection "rarely" successful with mssql_connect, with a MSSQL server under quite heavy load).

Happens only with PHP on Windows, not on Linux (FreeDTS).

But for some reason I needed to connect from PHP/Windows, so I have used the "ADO workaround", as previously suggested by alfa77.

At first, I didn't understand very well that workaround, so here are some details :

Do not use the ADOdb engine 'mssql' because it will still use mssql_connect(). Instead, use 'ado_mssql' which uses COM objects ; that makes all the difference.

Here is a basic database functions lib :

function db_open($db_host, $db_login, $db_pass, $db_name)
{
  $db = NewADOConnection('ado_mssql');
		
  $dsn="PROVIDER=MSDASQL;DRIVER={SQL Server};"
  . "SERVER=".$db_host.";DATABASE=".$db_name.";UID=".$db_login.";PWD=".$db_pass.";";
		
  $db->Connect($dsn);
		
  return $db;
}

function db_query($db, $query)
{
  return $db->Execute($query);
}
   
function db_fetch_assoc($res)
{
  $obj = $res->FetchNextObj();
  return get_object_vars($obj);
}
   
function db_close($db)
{
  $db->Close();
}

Same problem here.
Apache 2.2.10
Php 5.2.5 as module.
OS win2003 sp1+all critical updates

I even try upgrade to php 5.2.8, but it still appears.

I too have suffered this same problem for the last couple of years on all of the 5.x release of PHP.  It works great for days then has problem for a few days then works great.  1-3 page reloads often solves the problem but not always. Unfortunatley support for this extension has been discontinued--I wonder if this is one of the reasons why?  I would like to try using Microsofts SQLSRV driver but converting an entire website from mssql to sqlsrv is going to be a lot of work!

We're experiencing the same problem with Microsofts SQLSRV driver.
So it might be it's not just a driver problem.

trials

Related to Bug #35217.

Problem is due to connection limit. it would be good if you close connection once your done with sql part. use mssql_free_statement(resouceid) and connection close to db every page of you site.

I think that this bug is not related to connection limit.
I have closed each connection at the end of the script (although it is not necessary due to documentation: 
----------------------------
mssql_close <...>
Note that this isn't usually necessary, as non-persistent open links are automatically closed at the end of the script's execution. 
----------------------------
Also, exec sp_who2 did not show a lot of connections (no more than 200).

I have solved this problem by using another extension (odbtp as a gateway on Windows server, PHP is hosted now on UNIX) - everything is all right now.

You should really move to 5.3+ and use http://pecl.php.net/sqlsrv