Récupération de données d'un formulaire PHP/JavaScript - Page 2

(function (){
	var champs = [
		"prenom",
		"nom",
		"date_de_naissance",
		"url_photo"
	],
	
	ajouter_ligne = document.getElementById("ajouter_ligne"),
	table = document.getElementById("acteurs"),
	form = document.getElementById("form_acteurs");
	
		ajouter_ligne.onclick = function (){
		var i, supprimer,
		tbody = table.tBodies[0],
		ligne = tbody.insertRow(-1);

		function champ (name, value) {
			var t = document.createElement("input");
			t.type = "text";
			t.name = t.id = name +"[]";
			t.value = value || "";
        return t;
		}

		for (i = 0; i < champs.length; i++) {
			(ligne.insertCell(i)).appendChild(champ(champs[i]));
		}

		supprimer = document.createElement("button");
		supprimer.type = "button";
		supprimer.className = "del";
		supprimer.innerHTML = "×";
		supprimer.onclick = function (){
			var tr = this.parentNode.parentNode;
			index = tr.sectionRowIndex;
			tbody.deleteRow(index);
			valider.disabled = false;
			modifier.disabled = true;
		};
 
		i = ligne.insertCell(champs.length);
		i.className = "actions";
		i.appendChild(supprimer);

		var n, nt, inputs, index;
		for (var n = 0, nt = tbody.rows.length; n < nt; n++) {
			inputs = tbody.rows[n].getElementsByTagName("input");
			index = tbody.rows[n].sectionRowIndex;
			for (var nn = 0, ntn = inputs.length; nn < ntn; nn++) {
				inputs[nn].id = inputs[nn].name = inputs[nn].name.replace(/\[\d*\]$/, "["+index+"]");
			}
		}
	};
})();

<input type="text" name="prenom[]">
<input type="text" name="nom[]">
<input type="date" name="datenaissance[]">
<input type="text" name="url[]">

var champs = [
		"prenom",
		"nom",
		"date_de_naissance",
		"url_photo"
	],

function champ (name, value) {
			var t = document.createElement("input");
			t.type = "date";
			t.name = t.id = name +"[]";
			t.value = value || "";
        return t;
		}

		for (i = 0; i < champs.length; i++) {
			(ligne.insertCell(i)).appendChild(champ(champs[i]));
		}

$prenom = !empty($_POST['prenom']) 
?  $_POST['prenom'] : null;
foreach($prenom as $ligne => $P ){
 echo $ligne . " : " . $P . "<br>";
}