Qiita API を使うときには User-Agent を設定しないと 500 Internal Server Error が発生する ref: http://qiita.com/kobake@github/items/d256fd1665284fd3c65a

file1.txt

$ php QiitaApiSimple.php

Warning: file_get_contents(https://qiita.com/api/v1/items): failed to open stream: HTTP request failed! HTTP/1.1 500 Internal Server Error
 in QiitaApiSimple.php on line 3

Call Stack:
    0.0000     338728   1. {main}() QiitaApiSimple.php:0
    0.0000     338880   2. file_get_contents() QiitaApiSimple.php:3

PHP Warning:  file_get_contents(https://qiita.com/api/v1/items): failed to open stream: HTTP request failed! HTTP/1.1 500 Internal Server Error
 in QiitaApiSimple.php on line 3
PHP Stack trace:
PHP   1. {main}() QiitaApiSimple.php:0
PHP   2. file_get_contents() QiitaApiSimple.php:3

php

<?php
$url = 'https://qiita.com/api/v1/items';
$opts = array(
    'http'=>array(
        'method'=> "GET",
        'header'=> "User-Agent: OreOreAgent\r\n"
    )
);
$context = stream_context_create($opts);
$response = file_get_contents($url, false, $context);

php.ini

user_agent='OreOreAgent' (追記)

php:QiitaApiAgent.php

<?php
$url = 'https://qiita.com/api/v1/items';
$opts = array(
    'http'=>array(
        'method'=> "GET",
        'header'=> "User-Agent: OreOreAgent\r\n"
    )
);
$context = stream_context_create($opts);
$response = file_get_contents($url, false, $context);

QiitaApiAgent1.php

<?php
ini_set('user_agent', 'OreOreAgent');
$url = 'https://qiita.com/api/v1/items';
$response = file_get_contents($url);

QiitaApiSimple.php

<?php
$url = 'https://qiita.com/api/v1/items';
$response = file_get_contents($url);