d3 means of reading proxy data via PHP - php

Question

In the existing SO literature, I have seen examples that use jquery and PHP to proxy data:
jquery
function loadTheUrl(x){
$.ajax({ url: 'loader.php',
data: {url: x},
type: 'get',
success: function(output) {
$('.loading-space').html(output);
}
});
}
PHP
<?php
$doc = new DOMDocument();
$doc->loadHTML(file_get_contents($_GET['https://www.google.com/finance/getprices?q=.NSEI&x=NSE&i=600&p=1d&f=d,o']));
echo $doc->saveHTML();
Here is what the first few lines of the data look like at the URL seen in the PHP above. It is a page of plain text only, like this:
MARKET_OPEN_MINUTE=570
MARKET_CLOSE_MINUTE=960
INTERVAL=300
COLUMNS=DATE,OPEN
DATA=
TIMEZONE_OFFSET=-240
a1521120900,555.45
1,554.53
2,554.07
3,553.9
4,552.67
...
As far as I know, the PHP is correct. For my use case, I need to replicate the above jquery by means of d3. I was hoping that d3 would have something to use to interface with the data my php file is spitting out.
If you are wondering why I am going to such lengths, it's because my browsers are not letting me run scripts (i.e. d3.text(), d3.csv() et all) directly by say d3.text('https://www.google.com/finance...') due to the infamous access control origin header error. So my plan is to mirror the data from the google backfill off a local php file that I'm serving from my server. This way everybody is happy (or at least me).
When I try calling d3.text() on my php file, my data was not loaded correctly. In other words I tried: d3.text('my_loader.php'). But that resulted in lots of NaN errors, which I usually noticed are symptoms of a parsing error of some sort. Checking back through my code, things seem fine though. I have unary parsing in place, the strings should be cast to numbers. In fact, everything was working fine offline. I could load and parse the data directly when in my IDE. It was only when I published my d3 graph to the web did I realize I couldn't parse data from different origins. This is the point where I added the PHP component. My hunch was that d3 was actually trying to parse my PHP page and not the URL the PHP was pointing to. I later confirmed this by passing the data returned by d3.text() in the console and it was indeed the PHP page itself.
Question: In light of my cross-origin data situation, what can I do from the d3 side or the PHP side to make the two interface with each other correctly? I wonder if d3 is only suited for same origin data, or if there actually is a method to read/parse cross-origin data using a technique I'm not aware of (PHP or otherwise).

Answer 1

The url you are fetching does not exist within the $_GET variable.
The parameters you are submitting are an array:
$_GET = ['url' => 'some_url'];
Which means this:
$_GET['https://www.google.com/finance/getprices?q=.NSEI&x=NSE&i=600&p=1d&f=d,o]
is wrong (it's also missing a quote mark at the end of the string).
It should be $_GET['url']
With no validation:
<?php
header('Content-Type: text/plain');
echo file_get_contents($_GET['url']);
But that's neither here nor there.
The issue, I think, is with the url being passed. It contains a question mark and multiple ampersands (? and &). I think this is bjorking up the $_GET parameter so all you're getting is https://www.google.com/finance/getprices?q=.NSEI. You need to wrap the url in encodeURIComponent:
var url = encodeURIComponent('https://www.google.com/finance/getprices?q=.NSEI&x=NSE&i=600&p=1d&f=d,o');
d3.text('/path/to/myscript.php?url=' + url);

Answer 2

Cross origin applies to all ajax requests, instead of requesting d3.text('https://www.google.com/finance...') why not try d3.text('mymethod.php') and make sure the method returns a text file rather than html via the headers:
<?php
header('Content-Type: text/plain');
$file = file_get_contents('https://www.google.com/finance/getprices?q=.NSEI&x=NSE&i=600&p=1d&f=d,o');
echo $file;