Unfortunate that pg_fetch_all_columns() doesn't support fetching a column by its name -- if you want to do that, you'll need to use pg_field_num() as an intermediary:

For example:

<?php

if ($foo)
  $cols = "email_address";

else
  $cols = "last_name, middle_init";

$result = pg_query("Select first_name, $info, birthday from users_table");

// Problem -- does column #2 refer to the 'birthday' or 'middle_init' field?
$array = pg_fetch_all_columns($result, 2);

// Won't work, must use a column number instead of its name
$array = pg_fetch_all_columns($result, 'birthday');

// Works
$array = pg_fetch_all_columns($result, pg_field_num($result, 'birthday'));

?>

pg_fetch_all_columns() returns array (empty array) even if the result set in empty (while pg_fetch_all() returns FALSE when the result set is empty)

<?
$result = pg_query("
    SELECT 'something'
    WHERE 1 = 2
");
var_dump( pg_fetch_all($result) ); // boolean false
var_dump( pg_fetch_all_columns($result) ); // array(0){}
?>

php 4 equivalent:

<?php 
$conn = pg_pconnect("dbname=publisher");
if (!$conn) {
  echo "An error occured.\n";
  exit;
}

$result = pg_query($conn, "SELECT title, name, address FROM authors");
if (!$result) {
  echo "An error occured.\n";
  exit;
}

// Get an array of all author names
$arr = array();
while ($line = pg_fetch_array($result)) {
  array_push($arr, $line['name']);
}

var_dump($arr);

?>