Trying to create and echo array via pg_query_params - php

Question

I've worked with Postgresql some, but I'm still a novice. I usually default to creating way too many queries and hacking my way through to get the result I need from a query. This time I'd like to write some more streamlined code since I'll be dealing with a large database, and the code needs to be as concise as possible.
So I have a lot of point data, and then I have many counties. I have two tables, "counties" and "ltg_data" (the many points). My goal is to read through a specified number of counties (as given in an array) and determine how many points fall in each county. My novice, repetitive and inefficient way of doing this is by writing queries like this:
$klamath_40_days = pg_query($conn, "SELECT countyname, time from counties, ltg_data where st_contains(counties.the_geom, ltg_data.ltg_geom) and countyname");
$klamath_rows = pg_num_rows($klamath_40_days);
If I run a separate query like the above for each county, it gives me nice output, but it's repetitive and inefficient. I'd much rather use a loop. And eventually I'll need to pass params into the query via the URL. When I try to run a for loop in PHP, I get errors saying "query failed: ERROR: column "jackson" does not exist", etc. Here's the loop:
$counties = array ('Jackson', 'Klamath');
foreach ($counties as $i) {
echo "$i<br>";
$jackson_24 = pg_query($conn, "SELECT countyname, time from counties, ltg_data where st_contains(counties.the_geom, ltg_data.ltg_geom) and countyname = ".$i." and time >= (NOW() - '40 DAY'::INTERVAL)");
$jackson_rows = pg_num_rows($result);
}
echo "$jackson_rows";
So then I researched the pg_query_params feature in PHP, and I thought this would help. But I run this script:
$counties = array('Jackson', 'Josephine', 'Curry', 'Siskiyou', 'Modoc', 'Coos', 'Douglas', 'Klamath', 'Lake');
$query = "SELECT countyname, time from counties, ltg_data where st_contains(counties.the_geom, ltg_data.ltg_geom) and countyname = $1 and time >= (NOW() - '40 DAY'::INTERVAL)";
$result = pg_query_params($conn, $query, $counties);
And I get this error: Query failed: ERROR: bind message supplies 9 parameters, but prepared statement "" requires 1 in
So I'm basically wondering what the best way to pass parameters (either individual from perhaps a URL passed param or multiple elements in an array) to a postgresql query is? And then I'd like to echo out the summary results in an organized manner.
Thanks for any help with this.

Answer 1

If you just need to know how many points fall into each county specified in an array, then you can do the following in a single call to the database:
SELECT countyname, count(*)
FROM counties
JOIN ltg_data ON ST_contains(counties.the_geom, ltg_data.ltg_geom)
WHERE countyname = ANY ($counties)
AND time >= now() - interval '40 days'
GROUP BY countyname;
This is much more efficient than making individual calls and you return only a single instance of the county name, rather than one for every record that is retrieved. If you have, say 1,000 points in the country Klamath, you return the string "Klamath" just once, instead of 1,000 times. Also, php doesn't have to count the length of the query result. All in all much cleaner and faster.
Note also the JOIN syntax in combination with the PostGIS function call.

Answer 2

To execute a query with a parameter in a loop for several values you can use the following pattern:
$counties = array('Jackson', 'Josephine', 'Curry');
$query = "SELECT countyname, time from counties where countyname = $1";
foreach ($counties as $county) {
$result = pg_query_params($conn, $query, array($county));
$row = pg_fetch_row($result);
echo "$row[0] $row[1] \n";
}
Note that the third parameter of pg_query_params() is an array, hence you must put array($county) even though there is only one parameter.
You can also execute one query with an array as parameter.
In this case you should use postgres syntax for an array and pass it to the query as a text variable.
$counties = "array['Jackson', 'Josephine', 'Curry']";
$query = "SELECT countyname, time from counties where countyname = any ($counties)";
echo "$query\n\n";
$result = pg_query($conn, $query);
while ($row = pg_fetch_row($result)) {
echo "$row[0] $row[1] \n";
}