in_array() on multidimensional array

I want to find an array inside an array by its value.

Example:
It returns "Match not found", while "Peter" is inside the $people array.
But I can found "Joe".

$people = array(
  "Peter" => array (
        "test" => 0
    ),
  "Joe"
);

if (in_array("Peter", $people))
  {
     echo "Match found";
  }
else
  {
     echo "Match not found";
  }

How can I found "Peter" in the array?

>Solution :

Using in_array search for values, but in your code Peter is a key. Then you can use array_key_exists instead:

$people = array(
    "Peter" => array (
        "test" => 0
    ),
    "Joe"
);

if (array_key_exists("Peter", $people))
{
    echo "Match found";
}
else
{
    echo "Match not found";
}

Output

Match found

you can combine both since the name you’re searching is sometimes the value like "Joe" in your example.

if (array_key_exists("Peter", $people) || in_array("Peter", $people)) {
    echo "Match found";
} else {
    echo "Match not found";
}