inserting many rows

I will need to insert multiple rows into a table from php.
The data will come in 'packages' of 50-500 rows (they are responses from
different questionnaires). As there will be many people sending their
results in at the same time I need an effective method for this.

What do you suggest is the most effective way to insert this type of
data into the db? Issuing multiple inserts from php seems to be a waste
of resources.

I was thinking of writing the responses into a pg array field with a
single insert and than explode the content of that field into rows with
a function.

Could you suggest an efficient aproach?
Thanks for the help.

Balazs