View difference between Paste ID: EDuY2Cfu and HrXpgijn

 <?php
 
 /**
  * 呼叫 flickr.people.getPublicPhotos
  * @param string $user_id 要傳回照片的user id
  * @return string json格式的字串
  */
 function getPublicPhotos($user_id) {
     $ch = curl_init();
     //產生API網址，有部分參數在此寫死，例如輸出格式這邊是直接設定為JSON
     $api_key = '3dd490cec911376eb3356af84efc05e6';
     $url = "https://api.flickr.com/services/rest/?method=flickr.people.getPublicPhotos&api_key={$api_key}&user_id={$user_id}&format=json&nojsoncallback=1";
     $options = array(
         CURLOPT_URL => $url,
         CURLOPT_HEADER => false,
         CURLOPT_RETURNTRANSFER => true,
             //CURLOPT_SSL_VERIFYHOST => 0,
             //CURLOPT_SSL_VERIFYPEER => 0,
     );
     curl_setopt_array($ch, $options);
     $result = curl_exec($ch);
     curl_close($ch);
     return $result;
 }
 
 //檢查是否有GET的user_id參數
-if (isset($_GET['user_id'])) {
+if (isset($_GET['user_id']) and !empty($_GET['user_id'])) {
     $user_id = $_GET['user_id'];
     $data = getPublicPhotos($user_id);
     $json = json_decode($data, true);
-    $photos = $json['photos'];
+    $photos = $json['photos']['photo'];
 } else {
     $photos = array();
 }
 ?>
 
 <html>
     <head></head>
     <body>
         <form method="get">
             <label>user_id <input type="text" name="user_id" value="<?php echo isset($_GET['user_id']) ? $_GET['user_id'] : ''; ?>"></label>
             <input type="submit">
         </form>
         <div>
             <?php
-            foreach ($photos['photo'] as &$photo) {
+            foreach ($photos as &$photo) {
                 //產生flickr的連結
                 $url = "https://www.flickr.com/photos/{$photo['owner']}/{$photo['id']}";
                 //產生照片的連結
                 $img = "http://www.flickr.com/photos/{$photo['id']}_{$photo['secret']}.jpg";
                 //另一種產生照片連結的方法
                 //$img = "https://farm{$photo['farm']}.staticflickr.com/{$photo['server']}/{$photo['id']}_{$photo['secret']}.jpg";
                 echo "<a href=\"$url\" target=\"_blank\"><img src=\"{$img}\" border=\"0\"></a>\n";
             }
             ?>
         </div>
     </body>
 </html>