I'm trying to validate a simple schema against large JSON data. I only need to find if the properties I'm using in my PHP code are present in the JSON data. I've looked at several libraries but they seem overkill since they even validate the data type and I only need the presence of properties.

For example:
PHP variables I use: `name, age, gender`
JSON Data:

```
{
  "Location": "10.2.00",
  "Name": "Foo",
  "Age": "30",
  "Race": "NA",
  "Gender": "Male"
}

```

So there could be extra data in JSON.

**How can I check for the presence of JSON variables in my PHP code or another JSON schema?**