The following code will show you the details of a logged in customer.
<?php
$magentoURL = "http://127.0.0.1/mage2/";
$apiURL = $magentoURL."index.php/rest/V1/integration/customer/token";
$data = array("username" => "Test.User1521623008@phpcodez.com", "password" => "phpcodez&");
$data_string = json_encode($data);
$ch = curl_init($apiURL);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, array("Content-Type: application/json","Content-Length: ".strlen($data_string)));
$token = curl_exec($ch);
$headers = array("Authorization: Bearer ".json_decode($token));
$requestUrl =$magentoURL.'index.php/rest/V1/customers/me';
$ch = curl_init($requestUrl);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$result = curl_exec($ch);
//decoding result
$result= json_decode($result);
//printing result
echo "<pre>";print_r($result);
?>