Code to support oauth2 properties that are an array of things.

oauth2_moodle_user_map_array.php

<?php
$map = [
    'otherMails-0' => 'email'
];
$userinfo = json_decode('{
    "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users(*)/$entity",
    "otherMails": [
    	"0@",
    	"1",
    	"2"
    ],
    "displayName": "Megan Bowen",
    "givenName": "Megan",
    "jobTitle": "Auditor",
    "mail": "[email protected]",
    "mobilePhone": null,
    "officeLocation": "12/1110",
    "preferredLanguage": "en-US",
    "test": {
    	"foo": "bar",
    	"bar": "foo"
    },
    "surname": "Bowen",
    "userPrincipalName": "[email protected]",
    "id": "48d31887-5fad-4d73-a9f5-3c356e68a038"
}');
$user = new stdClass();
foreach ($map as $openidproperty => $moodleproperty) {
    // We support nested objects via a-b-c syntax.
    $getfunc = function($obj, $prop) use (&$getfunc) {
                   $proplist = explode('-', $prop, 2); 
                   if (is_array($obj) && count($obj) > 0) {
                   		if (count($proplist) > 1) {
                   			return $getfunc($obj, $proplist[0]);
                   		}
                   		return $obj[$proplist[0]];
                   }

                   if ((empty($proplist[0]) || empty($obj->{$proplist[0]}))) {
                       return false;
                   }
                   $obj = $obj->{$proplist[0]};
                   if (count($proplist) > 1) {
                       return $getfunc($obj, $proplist[1]);
                   }
                   return $obj;
    };

    $resolved = $getfunc($userinfo, $openidproperty);
    if (!empty($resolved)) {
        $user->$moodleproperty = $resolved;
    }
}

var_dump($user);