Where in clause

Thank you. I have one more issue.

the following filter works when using the api docs on my example_relationship table:
(example_field=example) and (example_field2=(10))

but when written down in a php server script like this :

$var1 = "example";
$var2 = 10 ;
$filterData = ["filter" => '(example_field='.$var1.')) AND (example_field2=('.$var2.'))' ];
$tableGetCall = $get("mysql/_table/example_relationship" , $filterData);

It only returns values as if AND clause wasn't there. It only matches example_field=example.

Thank you.