当我应用array_key_exists函数时，它不会从JSON返回值

Question

I am using PHP to get data from JSON and when i test the key in JSON with array_key_exists to make sure it exists it returns nothing. Here is the link to the library: https://api.edmunds.com/api/vehicle/v2/vins/4T1BK1EB6DU056165?&fmt=json&api_key=zzasv56vxwkx67m9cy6apfmq When i try to run it like this i get nothing:

if(array_key_exists('years[0]->year', $jfo)) {
$mds = $jfo->years[0]->year;

}else{
$mds="mds not found";
}

And this way it works:

$mds = $jfo->years[0]->year;

Answer 1

Assuming that you are sure that the value will not be NULL when set, you would be better served with isset() . Something like

if( isset($jfo->years) 
    && is_array($jfo->years) 
    && isset($jfo->years[0]->year)
){
    $mds = $jfo->years[0]->year;
}else{
    $mds = 'mds not found';
}

Or if you wanted to be less verbose and know for sure that $jfo->years will be an array.

$mds = isset($jfo->years[0]->year) ? $jfo->years[0]->year : 'mds not found';

Or if you are running php>=7 and want to be even less verbose.

$mds = $jfo->years[0]->year ?? 'mds not found';