смотря на чем писать приложение... я бы сделал так:
perl:
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#!/usr/bin/perl -w
use strict;
use CGI qw(:standard);
use SQLayer;
my $D = SQLayer -> new(database => \'DBI:mysql:database=phorum;host=localhost;port=3306\', user => \'user\', passoword => \'somepass\');
my $now_day=time;
$now_day-=86400;
my ($day,$mon,$year,$wday) = ((localtime($now_day))[3,4,5,6]);
$year+=1900;
$mon+=1;
my $month = $mon;
$day = 31;
if($month==4 || $month==6 || $month==9 || $month==11) {$day=30;}
elsif( $month==2)
{
if($year%4==0){$day=29;}
else {$day=28;}
}
$mon_begin = sprintf("%04d-%02d-%02d", $year, $mon, 1);
$mon_end = sprintf("%04d-%02d-%02d", $year, $mon, $day);
my @users=$D->column("SELECT user_id FROM user WHERE date>=\'$mon_begin\' AND date <=\'$mon_end\'");
my $NUM=scalar(@users);
print "Content-type: text/html\\n\\n";
print "Кол-во человек за текущий месяц: $NUM";
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