// présentation 1
$depts = array();
$depts["01"] = "01 - Ain";
$depts["02"] = "02 - Aisne";
$depts["03"] = "03 - Allier";
$depts["04"] = "04 - Alpes de Haute Provence";
$depts["05"] = "05 - Hautes Alpes";
$depts["06"] = "06 - Alpes Maritimes";
$depts["07"] = "07 - Ardèche";
$depts["08"] = "08 - Ardennes";
$depts["09"] = "09 - Ariège";
$depts["10"] = "10 - Aube";
$depts["11"] = "11 - Aude";
$depts["12"] = "12 - Aveyron";
$depts["13"] = "13 - Bouches du Rhône";
$depts["14"] = "14 - Calvados";
$depts["15"] = "15 - Cantal";
$depts["16"] = "16 - Charente";
$depts["17"] = "17 - Charente Maritime";
$depts["18"] = "18 - Cher";
$depts["19"] = "19 - Corrèze";
$depts["2A"] = "2A - Corse du Sud";
$depts["2B"] = "2B - Haute Corse";
$depts["21"] = "21 - Côte d'Or";
$depts["22"] = "22 - Côtes d'Armor";
$depts["23"] = "23 - Creuse";
$depts["24"] = "24 - Dordogne";
$depts["25"] = "25 - Doubs";
$depts["26"] = "26 - Drôme";
$depts["27"] = "27 - Eure";
$depts["28"] = "28 - Eure et Loir";
$depts["29"] = "29 - Finistère";
$depts["30"] = "30 - Gard";
$depts["31"] = "31 - Haute Garonne";
$depts["32"] = "32 - Gers";
$depts["33"] = "33 - Gironde";
$depts["34"] = "34 - Hérault";
$depts["35"] = "35 - Ille et Vilaine";
$depts["36"] = "36 - Indre";
$depts["37"] = "37 - Indre et Loire";
$depts["38"] = "38 - Isère";
$depts["39"] = "39 - Jura";
$depts["40"] = "40 - Landes";
$depts["41"] = "41 - Loir et Cher";
$depts["42"] = "42 - Loire";
$depts["43"] = "43 - Haute Loire";
$depts["44"] = "44 - Loire Atlantique";
$depts["45"] = "45 - Loiret";
$depts["46"] = "46 - Lot";
$depts["47"] = "47 - Lot et Garonne";
$depts["48"] = "48 - Lozère";
$depts["49"] = "49 - Maine et Loire";
$depts["50"] = "50 - Manche";
$depts["51"] = "51 - Marne";
$depts["52"] = "52 - Haute Marne";
$depts["53"] = "53 - Mayenne";
$depts["54"] = "54 - Meurthe et Moselle";
$depts["55"] = "55 - Meuse";
$depts["56"] = "56 - Morbihan";
$depts["57"] = "57 - Moselle";
$depts["58"] = "58 - Nièvre";
$depts["59"] = "59 - Nord";
$depts["60"] = "60 - Oise";
$depts["61"] = "61 - Orne";
$depts["62"] = "62 - Pas de Calais";
$depts["63"] = "63 - Puy de Dôme";
$depts["64"] = "64 - Pyrénées Atlantiques";
$depts["65"] = "65 - Hautes Pyrénées";
$depts["66"] = "66 - Pyrénées Orientales";
$depts["67"] = "67 - Bas Rhin";
$depts["68"] = "68 - Haut Rhin";
$depts["69"] = "69 - Rhône";
$depts["70"] = "70 - Haute Saône";
$depts["71"] = "71 - Saône et Loire";
$depts["72"] = "72 - Sarthe";
$depts["73"] = "73 - Savoie";
$depts["74"] = "74 - Haute Savoie";
$depts["75"] = "75 - Paris";
$depts["76"] = "76 - Seine Maritime";
$depts["77"] = "77 - Seine et Marne";
$depts["78"] = "78 - Yvelines";
$depts["79"] = "79 - Deux Sèvres";
$depts["80"] = "80 - Somme";
$depts["81"] = "81 - Tarn";
$depts["82"] = "82 - Tarn et Garonne";
$depts["83"] = "83 - Var";
$depts["84"] = "84 - Vaucluse";
$depts["85"] = "85 - Vendée";
$depts["86"] = "86 - Vienne";
$depts["87"] = "87 - Haute Vienne";
$depts["88"] = "88 - Vosges";
$depts["89"] = "89 - Yonne";
$depts["90"] = "90 - Territoire de Belfort";
$depts["91"] = "91 - Essonne";
$depts["92"] = "92 - Hauts de Seine";
$depts["93"] = "93 - Seine St Denis";
$depts["94"] = "94 - Val de Marne";
$depts["95"] = "95 - Val d'Oise";
$depts["97"] = "97 - DOM";

<?php
function get_interest_factor($year_term, $monthly_interest_rate) {
	global $base_rate;
	$factor      = 0;
	$base_rate   = 1 + $monthly_interest_rate;
	$denominator = $base_rate;
	for ($i=0; $i &lt; ($year_term * 12); $i++) {
		$factor += (1 / $denominator);
		$denominator *= $base_rate;
	}
	return $factor;
}
?>

<?php
$calcul = get_interest_factor($year_term, $monthly_interest_rate);
$mensualite = $year_term / $calcul;
?>

<?php
//Montant de la somme de l'emprunt
$somme_emprunte = 1000;
//Durée du prêt en années
$annee = 30;
//Taux annuel du prêt
$taux = 2.8;
// reste plus qu'à savoir combien vous allez payer par mois :
$mensualite = $annee / get_interest_factor($annee, $taux/1200);
?>