mssql php returns false, after REPLACE it works

I have a strange error:

$stmt = 'SELECT field FROM table';
// returns "false"

$stmt = 'SELECT REPLACE(field, ' ', ' ') AS field FROM table';
// returns the correct value

Does anyone know why this behavior occurs? (“field” is just a varchar column)

If I execute the same statement in the SQL-Editor it works fine. It only occurs with my PHP / MSSQL Setup.

Thats my setup:
DB Server: a Ubuntu server with mssql installed (https://learn.microsoft.com/en-us/sql/linux/quickstart-install-connect-ubuntu?view=sql-server-ver16)

PHP Server: Server with PHP that connects to the DB server via sqlsrv_connect().

Is there any setting I can check or do you have any documentation I can look up?