<?php

$donnees = array(
    "Jean" => array(
        "nom" => "Dupont",
        "email" => "jean.dupont@outlook.com"
    ),
    "Pierre" => array(
        "nom" => "Martin",
        "email" => "p.mart1@gmail.com"
    ),
    "Paul" => array(
        "nom" => "Durand",
        "email" => "durandpaul@caramail.fr"
    ),
);

foreach ($donnees as $prenom => $info) {
    $data = $prenom . " " . $info["nom"] . " " . $info["email"];
    file_put_contents("data1.txt", $data . PHP_EOL, FILE_APPEND);
    echo "Ecriture de $prenom dans le fichier data1.txt<br/>";
}