Call to undefined function odbc_connect() in Ubuntu - php

Question

I am trying to connect with PHP to SQL server. I have installed Microsoft ODBC Driver 13 for SQL Server and I have test it using 'isql' command. Now when I am trying to connect to the server in PHP it always crashes and says "http error 500". Here is the code:
<?php
$server = merkur.edikt.local;
$database = ITServiceE;
$connection = odbc_connect("Driver={ODBC DRIVER 13 for SQL Server};
Server=$server;Database=$database;",
'user',
'PW'
);
echo "connected";
?>
I am using Ubuntu 16.04 server and Apache2 and PHP 7.
I think it might be problem with permissions for the Apache(if the Apache can access the ODBC Driver) but I am not really sure how this works.
EDIT:
Here is the log from Apache errors:
PHP Notice: Use of undefined constant merkur - assumed 'merkur' in /var/www/html/index.php on line 2
PHP Notice: Use of undefined constant edikt - assumed 'edikt' in /var/www/html/index.php on line 2
PHP Notice: Use of undefined constant local - assumed 'local' in /var/www/html/index.php on line 2
PHP Notice: Use of undefined constant ITServiceE - assumed 'ITServiceE' in /var/www/html/index.php on line 3
PHP Fatal error: Uncaught Error: Call to undefined function odbc_connect() in /var/www/html/index.php:4\nStack trace:\n#0 {main}\n thrown in /var/www/html/index.php on line 4
and the file odbc.ini is empty and odbcinst.ini looks like this:
[ODBC Driver 13 for SQL Server]
Description=Microsoft ODBC Driver 13 for SQL Server
Driver=/opt/microsoft/msodbcsql/lib64/libmsodbcsql-13.0.so.0.0
Threading=1
UsageCount=2

Answer 1

Call to undefined function odbc_connect() means that your PHP system doesn't have any function with that name.
Since it isn't a user function written in pure PHP but a function from a PHP extension, that means that you haven't installed such extension. It's worth noting that the PHP extensions is not the same as the SQL Server driver (you need both).
Your code also contains some undefined constants which I guess are meant to be strings. I strongly recommend you enable full error reporting in your development box so you don't need to check the error logs to learn about simple errors.