Hi,
The function to export data in formats " COPY " and " SQL" is not working in phpPgAdmin 5.1 (PHP 7.0.4-7ubuntu2 ) with PostgreSQL 9.5.2 .
I found the error on line 76 of dbexport.php file, the ' -i' option is marked as deprecated since version 9.1 of PostgreSQL
https://www.postgresql.org/docs/9.1/static/app-pgdump.html
Removing this option, the dump back to function normally.
Francisco AC Lima