Write postgres output to a file using php - php

Question

I want to get the output of a postgres query written into a file. I am using php to connect to the remote database and execute the query. Here is the sample code.
$connection_id=pg_connect("host=localhost dbname=test user=test password=test");
$psql="select example from sample limit 180";
$result=pg_query($connection_id,$psql);
I have the query executed, but I am unable to write it to a file. How do I do that?
Help is really appreciated.

Answer 1

You cannot write the query result into a file directly. The result returned by pg_query is no string with any data that can be printed or written into a file. It's either an error status (false) or some kind of "reference" to result data kept for this query.
If $result isn't ==false and if PostgreSQL could find any rows as a result for your query, then you can fetch these rows. But that's an extra step. It's not included in pg_query. In order to check how many result rows were found you can use the function pg_num_rows.
Then you can iterate through the result set using pg_fetch_assoc. This is only one suitable function. There are a few more, e.g. pg_fetch_row.
Here's some small example code (quick & dirty without much error handling):
<?php
// Set the output of this script to plain text
header("Content-Type: text/plain");
$conn = pg_connect("..."); // insert your data here
if (!$conn) die ("Couldn't connect.");
$result = pg_query($conn, "SELECT example FROM ..."); // TODO
// Check for error and check the number of rows found:
if ((!$result) || (pg_num_rows($result) < 1)) {
pg_close();
echo "Couldn't find any data for your query. Maybe the query is wrong (error) or there are no matching lines.";
exit;
}
// Line counter for screen output
$i = 1;
// Open file. (Important: Script must have write permission for the directory!)
$fileHandle = fopen("./myresults.txt", "w");
// Do this as long as you can find more result rows:
while ($row = pg_fetch_assoc($result)) {
// Write value to the output that is sent to the web browser client:
echo "Line " . $i . ": \"" . strip_tags($row['example']) . "\"\r\n";
// Write the same value as a new line into the opened file:
fwrite ($fileHandle, $row['example'] . "\r\n";
// Increase line number counter:
$i++;
}
// Close the file:
fclose ($fileHandle);
// Free the result / used memory:
pg_free_result($result);
pg_close();
?>