Description:
------------
MS-SQL driver version or file name: php_pdo_sqlsrv_71_nts.dll - File version 4.1.8.9607 (32 bit)
SQL Server version: Microsoft SQL Server Express (64-bit) - 13.0.4206.0
Client operating system: Windows Server 2012 64-bit
PHP version: 7.1
Microsoft ODBC Driver version: 13

I'm upgrading an existing website from PHP v5.6 to v7.1. The only changes are the PHP version and the version of the MS-SQL PHP drivers.

Everything works as expected (as per previous site), except when I enable Zend opcache in php.ini. When I enable it, the site returns one of two error messages:

SQLSTATE[08001]: [Microsoft][ODBC Driver 13 for SQL Server]SQL Server Network Interfaces: Not enough storage is available to process this command. 1
or occasionally
Fatal error: No ODBC error was found 

The existing PHP v5.6 site has opcache enabled using MS-SQL drivers and does not return errors. Changing opcache settings in PHP v7.1 has no effect on the errors. If I disable Zend opcache, the errors disappear.  They only present themselves when opcache is enabled.


Test script:
---------------
try {
$conn = new PDO('sqlsrv:server='.MSSQL_SERVER.'; Database='.MSSQL_DB, MSSQL_USER, MSSQL_PWD);
$conn->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING );
}
catch(Exception $e)
{ die( print_r( $e->getMessage() ) ); }