Getting an uncaught exception in PHP when trying to get data from POST API

Question

I'm trying to access a list of most recent comments on Stack Overflow using this PHP:

<?php
    function do_post_request($url, $data, $optional_headers = null)
    {
      $params = array('http' => array(
                  'method' => 'POST',
                  'content' => $data
                ));
      if ($optional_headers !== null) {
        $params['http']['header'] = $optional_headers;
      }
      $ctx = stream_context_create($params);
      $fp = @fopen($url, 'rb', false, $ctx);
      if (!$fp) {
        throw new Exception("Problem with $url, $php_errormsg");
      }
      $response = @stream_get_contents($fp);
      if ($response === false) {
        throw new Exception("Problem reading data from $url, $php_errormsg");
      }
      return $response;
    }
    echo do_post_request("https://api.stackexchange.com/2.1/comments?order=desc&sort=creation&site=stackoverflow", "");
?>

However, when I run it, I get this error message:

$ php index.php 

PHP Notice:  Undefined variable: php_errormsg in /var/www/secomments/index.php on line 14
PHP Fatal error:  Uncaught exception 'Exception' with message 'Problem with https://api.stackexchange.com/2.1/comments?order=desc&sort=creation&site=stackoverflow, ' in /var/www/secomments/index.php:14
Stack trace:
#0 /var/www/secomments/index.php(22): do_post_request('https://api.sta...', '')
#1 {main}
  thrown in /var/www/secomments/index.php on line 14

Does anyone have any ideas as to what might be causing this, and what one would do to fix it?

Answer 1

The API, in this situation, should be called from the method get.

If you do visit the API at this link: https://api.stackexchange.com/2.1/comments?order=desc&sort=creation&site=stackoverflow
You are presented with a nice JSON with all the information you want.

If instead, you fix up the post params:

$params = array('http' => array(
    'method' => 'POST',
    'content' => $data,
    'header' => 'Content-Length: ' . strlen($data)
));

You are shown this instead:

{"error_id":404,"error_name":"no_method","error_message":"this method cannot be called this way"}

Hopefully you know that you can simply just use file_get_contents to contact the API with the traditional get.

$json = json_decode(file_get_contents("https://api.stackexchange.com/2.1/comments?order=desc&sort=creation&site=stackoverflow"), true);

Answer 2

As the error said php_errormsg is your problem.

You have to make sure errors are tracked before assuming php_errormsg is defined.

you should turn the track_errors configuration option on before trying to get the value of php_errormsg, example :

<?php
    function do_post_request($url, $data, $optional_headers = null)
    {
      error_reporting(E_ALL);
      ini_set('track_errors', 1);

       global $php_errormsg;

      $params = array('http' => array(
                  'method' => 'POST',
                  'content' => $data
                ));
      if ($optional_headers !== null) {
        $params['http']['header'] = $optional_headers;
      }
      $ctx = stream_context_create($params);
      $fp = @fopen($url, 'rb', false, $ctx);
      if (!$fp) {
        throw new Exception("Problem with $url, $php_errormsg");
      }
      $response = @stream_get_contents($fp);
      if ($response === false) {
        throw new Exception("Problem reading data from $url, $php_errormsg");
      }
      return $response;
    }
    echo do_post_request("https://api.stackexchange.com/2.1/comments?order=desc&sort=creation&site=stackoverflow", "");

EDIT:

Also in the php.ini conficuration file you can set :

track_errors = On

IMPORTANT: From the PHP website

While $php_errormsg is a global, it is not a superglobal.

You'll have to qualify it with a global keyword inside a function.

<?php function checkErrormsg() {
    global $php_errormsg;
    @strpos();
    return $php_errormsg; } ?>

EDIT 2 : USE of Global variable = bad practice link link