how to use nullif() in a query in a php form

Question

I try to import a csv file in a table in PostgreSQL 13 and php form ( beginner ).
There are two foreign keys integer type in the table, one can be empty. So when I import the file I have the common message invalid input syntax for type integer for one of them.
Following this post , NullIf() function seems to be a simple solution.

I can't find the right way to use it in:

$sql = "INSERT INTO activite.us (numus, gidgeo, gidaxe)
        VALUES ('".$getData[0]."','".$getData[10]."', NULLIF('".$getData[11]."', '') " ;

The foreign key is the last variable.

• I tried to replace second arg with NULL;
• I tried 'NULLIF("...")' and some others false combo.

How to fix that? Thanks.

Answer 1

(Even if PDO would be better,) an answer is

NULLIF('".$getData[11]."', '')::integer)