Sage One API Error - php

Question

I am using the SageOne API PHP Library. It works fine, but I get an error if I try to use get or post.
The error is,
Only variables should be passed by reference sage.api.php on line 130
My get request code is
$client = new SageOne(SAGE_CLIENT_ID, SAGE_CLIENT_SECRET);
$client->setAccessToken("c7c7547xxxxxxxxxxxx8efa4f5df08f750df");
$data = array( );
$result = "";
$client = $client->get('/products', $data);
I don’t know what’s wrong.
Full Code
require 'sage.api.php';
define('SAGE_CLIENT_ID', "fa1e8c1b114347a356d2");
define('SAGE_CLIENT_SECRET', "faaa7b353521f823ba13e3a20e72dd057c3a5fd1");
$client = new SageOne(SAGE_CLIENT_ID, SAGE_CLIENT_SECRET);
$callbackURL = 'xxxxx/addonmodules.php?module=sageone';
// We need to build the authorise url and redirect user to authorise our app
if(!$_GET['code']){
$authoriseURL = $client->getAuthoriseURL($callbackURL);
// redirect user
header("Location: ".$authoriseURL);
exit;
// We now have the authorisation code to retrieve the access token
} else {
$accessToken = $client->getAccessToken($_GET['code'], $callbackURL);
$token= $accessToken['access_token'];
$end = 'public';
$data ='';
$result = $client->get($end, $data);
echo '<pre>';
print_r($result);
Code Snippets from sage.api.php
class SageOne { ...
...
public function get($endpoint, $data=false){
return $this->call($endpoint, 'get', $data);
}
...
// error line 130 from this code
private function buildSignature($method, $url, $params, $nonce){
// uc method and append &
$signature = strtoupper($method).'&';
// percent encode bit of url before ? and append &
$signature .= rawurlencode(array_shift(explode('?', $url))).'&';
// percent encode any params and append &
if (is_array($params)){
// sort params alphabetically
$this->ksortRecursive($params);
// build query string from params, encode it and append &
$signature .= str_replace(
array('%2B'),
array('%2520'),
rawurlencode(http_build_query($params, '', '&'))
).'&';
// params can be string
} else {
// build query string from params, encode it and append &
$signature .= rawurlencode($params).'&';
}
// add 'nonce' - just use an md5
$signature .= $nonce;
// now generate signing key
$signingKey = rawurlencode($this->signingSecret).'&'.rawurlencode($this->accessToken);
// encode using sha 1, then base64 encode
$finalSignature = base64_encode(hash_hmac('sha1', $signature, $signingKey, true));
return $finalSignature;
}
This is the shortest i can make to see all important code

Answer 1

This is due to trying to return the result of a function or method directly to another function or method... the result doesn't have a reference.
So, for example:
$obj->method(doSomething(), 'asdf', 'qwerty');
The error means you should assign the value of doSomething() before passing it.
$result = doSomething();
$obj->method($result, 'asdf', 'qwerty');
Also see: Only variables should be passed by reference

Answer 2

A function (in this case, $client->get()) can be defined to receive its parameters by reference. This means that it can modify those parameters directly. So if you call $client->get($a, $b), the function may alter the values of $a and $b.
Clearly, it can only alter the values of variables, so when a function receives a parameter by reference, you must pass it a variable, not a string, an integer, or a direct call to another function.
So if the function $client->get() receives its first parameter by reference, none of the following can work:
$client->get('string', $data);
$client->get(15, $data); // int
$client->get(other_function_call(), $data);
$client->get(12.5, $data); // float
$client->get(array(), $data);
You have to do this:
$a = 'string';
$client->get($a, $data);
Or $a = whatever, be it a string, an int, a function call. The point is (and this is stated quite clearly in the error message) that you must pass a variable. So save whatever you want to pass as a variable, then pass that.