The code in php_odbc.c, that checks if a persistent connections still alive, when finds a bad connection will try to deallocate the connection twice causing Access Violation in SQLServer ODBC driver


zend_hash_del will make a call to _close_odbc_connection 
through destruction process. 

safe_odbc_disconnect(db_conn->hdbc);
SQLFreeConnect(db_conn->hdbc);

Aren't nessessary here and will cause Access Violation in SQLServer driver.

Line 2125 in php_odbc.c

if(ODBCG(check_persistent)){
RETCODE ret;
UCHAR d_name[32];
SWORD len;

ret = SQLGetInfo(db_conn->hdbc, SQL_DATA_SOURCE_READ_ONLY, d_name, sizeof(d_name), &len);

if(ret != SQL_SUCCESS || len == 0) {
zend_hash_del(&EG(persistent_list), hashed_details, hashed_len + 1);
safe_odbc_disconnect(db_conn->hdbc);
SQLFreeConnect(db_conn->hdbc);
goto try_and_get_another_connection;
}
}
}