如何获取JSON属性名称php

I have a folowing JSON file:

{"ver":2,"sb":[some array],"ld":[some array] ,"hd":[some array]}

I try to ger property names with next code:

$path='./datafiles/jsonTest.json';
$data = json_decode(file_get_contents($path));
$properties=get_object_vars($data);
foreach($properties as $propName){
    echo $propName.'<br>';
}

but as result I get:

2
Array
Array
Array

when I need:

'ver'
'sb'
'ld'
'hd'

Can someone help me? Thanks!

If you don't need the resulting output as an object, you coud use the array version of json_decode

$data = json_decode(file_get_contents($path), true);

$properties = array_keys($data);

Have you tried the key?

foreach($properties as $key => $propName){
    echo $key.'<br>';
}

you can also try using json_decode to give you an associative array

$path='./datafiles/jsonTest.json';
$data = json_decode(file_get_contents($path),true);
foreach($data as $name => $value){
    echo $name.'<br>';
}

You can either use reflection to get the properties names (http://php.net/manual/en/reflectionclass.getproperties.php) - which would be the elegant way - or you decide not to decode the Json data and extract the names and values with manual string operations.