Ionic 2 how to retrieve info in list? - ionic2

Question

I'm trying to retrieve the info from my PHP server.
Here is my code
//Dans mon service d'authentification
checkVehicleList() {
this.getUserId().then(data => {
this.userid = data;
return new Promise(resolve => {
alert(this.userid);
this.http.get('http://localhost/helloworld/api/v1/list?iduser='+this.userid).subscribe(data => {
alert(data.json().InformationsVehicules);
if(data.json().InformationsVehicules){
alert("reussite");
} else { alert("error !") }
});
});
});
}
//Dans la page des vehicules, j'appel la fonction juste pour savoir ce qu'elle qaffiche avec les alerts
public MarqueVeh : any;
public marque : any;
loadVeh() {
this.viauth.checkVehicleList().then(data => {
this.MarqueVeh = data;
});
}
// Voici le tableau que me retourne ma route PHP
{"InformationsVehicules":[{"marque":"bgy","matricule":"ce1370","numero_chassi":"123654"},{"marque":"bvd","matricule":"derty","numero_chassi":"ddff"}]}
I want the array that is returned to be kept in a variable so that I can use it like this
<ion-button button round class="veh-button" clear color="light" (click)="showVehiclePopUp()">{{Veh.marque}}<span style="display:inline-block; width: 200px;"></span>
<ion-buttons end>
<ion-icon name="ios-play"></ion-icon>
</ion-buttons></button><br>
I put the alerts in my code to know what the variables contain and I receive as message "undefiened".