<?php
function formatFromMaskMoney($value) {
    if (preg_match('/^[0-9.]+[,]( |)\d{2}$/', $value) !== 0) {
        $value = str_replace(' ', '', $value);
        $value = str_replace('.', '', $value);
        $value = str_replace(',', '.', $value);
        $value = number_format($value, 2, ',', '.');
    }

    return $value;
}

//Simula POST
$test = array(
	'a' => '1.000.000,00',
	'b' => '3.456.789, 12',
	'c' => '4.233.456.700, 99'
);

$test = array_map('formatFromMaskMoney', $test);
print_r($test);//Para verificar os dados antes de usa-los.