How to install Microsoft ODBC driver

There are two ways to establish a connection with MSSQL:

DBLIB

Configure alt-freeTDS:
Add to /opt/alt/freetds/etc/freetds.conf the following details about MSSQL:

[my_mssql]
    host = %IP%
    port = %PORT%

Then enable module for user pdo_dblib:

selectorctl -u %USERNAME% -v %PHP_VERSION% -e pdo_dblib

Use the following code to establish connection with MSSQL:

$dbh = new PDO("dblib:host=my_mssql;dbname=%DB_NAME%", "%DB_USER%", P.S: "%DB_PASS%");

Alternative way (without updating /opt/alt/freetds/etc/freetds.conf)

Use full connection string

$dbh = new PDO("dblib:host=%IP%;port=%PORT%;dbname=%DB_NAME%", "%DB_USER%", "%DB_PASS%");

Configure ODBC

In /etc/odbcinst.ini add FreeTDS driver details:

    [FreeTDS]
    Description = MS SQL database access with Free TDS
    Driver      = /opt/alt/freetds/usr/lib64/libtdsodbc.so
    Setup      = /usr/lib64/libtdsS.so
    UsageCount  = 1

    * For i386/i686 use lib instead of lib64 in paths

    To /etc/odbc.ini add details about MSSQL server:

    [mssql_odbc]
    Description            = MSSQL Server
    Driver                  = FreeTDS  //should have the same name as driver in /etc/odbcinst.ini
    Database                = %DB_NAME%
    Server                  = %IP%
    Port                    = %PORT%

Update CageFS:

cagefsctl --update-etc

Enable PHP extensions:

selectorctl -u %USERNAME% -v %PHP_VERSION% -e pdo_odbc,odbc

Add the following to the connection script:

$dbh = new PDO("odbc:mssql_odbc", "sa", "%DB_USER%", "%DB_PASS%");

Also, you need to perform the following:

/opt/alt/alt-php-config/install_odbc
cagefsctl --force-update
cagefsctl -M