json_encode creates useless zero keys - php

Question

I am writing an API to output an adress book, which I get the output as a XML. The output is JSON.
What's my problem?
I looping through the entries, which I get from an XML file and store it in an array. That means, that every entry includes an contact:
$xml = new SimpleXMLElement("adressbook.xml"); // <-- Only an example URL
$totalResults = $xml->children('openSearch', true)->totalResults;
$contacts=array();
foreach($xml->entry as $contact){
$tel = $contact->children('tel', true);
$entry = array(
"type"=>$tel->type,
"name"=>$tel->name,
"firstname"=>$tel->firstname,
"street"=>$tel->street,
"streetno"=>$tel->streetno,
"zip"=>$tel->zip,
"city"=>$tel->city,
"canton"=>$tel->canton,
"country"=>$tel->country,
"phone"=>$tel->phone
);
array_push($contacts,$entry);
}
After this I want to echo the array in json. I do this with json_encode.
But there is the problem. Instead of giving the results directly, it shows me following results:
The zero's which are red marked should not exist.
What I tried
I researched in the internet and found in the docs and in a few posts on Stack Overflow the JSON_FORCE_OBJECT attribute for json_encode.
http://php.net/manual/en/function.json-encode.php
Now my function looks like this:
echo json_encode($contacts,JSON_FORCE_OBJECT);
But I still get the zero's.
Here is also a small example of my XML:
<entry>
<updated>2017-04-11T02:00:00Z</updated>
<published>2017-04-11T02:00:00Z</published>
<title type="text">Mustermann, Max</title>
<tel:type>Person</tel:type>
<tel:name>Mustermann</tel:name>
<tel:firstname>Max</tel:firstname>
<tel:street>Musterstrasse</tel:street>
<tel:streetno>17</tel:streetno>
<tel:zip>8000</tel:zip>
<tel:city>Zürich</tel:city>
<tel:canton>ZH</tel:canton>
<tel:country>ch</tel:country>
<tel:phone>[phone]</tel:phone>
</entry>
What is going wrong?
UPDATE:
Here is the var_dump:
object(SimpleXMLElement)#6 (15) { ["type"]=> string(12) "Organisation" ["name"]=> string(28) "*******" ["occupation"]=> string(57) "*******" ["street"]=> string(11) "Musterstrasse" ["streetno"]=> string(1) "17" ["zip"]=> string(4) "8000" ["city"]=> string(5) "Zürich" ["canton"]=> string(2) "ZH" ["country"]=> string(2) "ch" ["phone"]=> string(12) "[phone]" }

Answer 1

One approach is to use strval to convert each object to a string
$xml = new SimpleXMLElement("adressbook.xml"); // <-- Only an example URL
$totalResults = $xml->children('openSearch', true)->totalResults;
$contacts=array();
foreach($xml->entry as $contact){
$tel = $contact->children('tel', true);
$entry = array(
"type"=>strval($tel->type),
"name"=>strval($tel->name),
"firstname"=>strval($tel->firstname,)
"street"=>strval($tel->street),
"streetno"=>strval($tel->streetno),
"zip"=>strval($tel->zip),
"city"=>strval($tel->city),
"canton"=>strval($tel->canton),
"country"=>strval($tel->country),
"phone"=>strval($tel->phone)
);
array_push($contacts,$entry);
}