PHP returns json PHP method to determine whether a json object exists

In the actual test, when PHP reads the json array and uses simple if or array_key_exists to determine whether the object exists, an error will be reported. The following is the correct judgment method from Google search

In fact, the error is reported because I am not very proficient in PHP. Maybe the correct judgment method I think is not the most perfect solution or even wrong. This blog post is reserved for my own use. Error code:

<span>$structure</span> = <span>imap_fetchstructure</span>(<span>$connection</span>, <span>$id</span>,<span> FT_UID);
</span><span>if</span> (<span>array_key_exists</span>('parts', <span>$structure</span><span>))
{
}</span>

An error will appear Warning: array_key_exists() expects parameter 2 to be array, boolean Given

The correct solution is:

<span>if</span> (<span>is_array</span>(<span>$structure</span>) && <span>array_key_exists</span>('parts', <span>$structure</span>)) <br>{ <span>//</span><span>...magic stuff here <br>}</span>

And another way is to use isset to directly judge:

<span>if</span>(<span>isset</span>(<span>$structure</span>['parts'<span>]))
 {
 }<br></span>

　 // Therefore, it is necessary to return TURE

only if the variable exists and the value is not NULL