how do i check if its in table with PHP?

[Anon]

I have a counter and I only want it to count unique hits. I have that everytime a user comes in, their IP goes into a table. I have a query to call all the values from the table using select. Now how do I use PHP to say

// part i need help

if ( [the value is in the table )

// part i have done
{
dont count
}
else
{
count
}

[Anon]

Do an update, if that fails, do an insert.

Chris