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Balderick

check if facebook user exists

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Can someone give any suggestion how to check if a facebook address is valid when send by form input?

I created a function checking the url address with get_headers at status code 302. This doesn't work when a facebook username doesn't exist, because it still gives true.

How to solve this problem?

 

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302 is a redirect.  I don't think redirect would be "true", I think that would be false.  Maybe you can check the location header to see where it's trying to redirect to and base your conclusion on that.

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this is a part of the code:

<?php 


	$url_inp = 'http://www.facebook.com/thisisnothingbutcrap';

	$array = get_headers($url_inp);
		
	$string = $array[0];
	//    if( strpos($string,"200") || strpos($string,"301") || strpos($string,"302") || strpos($string,"403")   ) {
	 if(  strpos($string,"302")    ) {  
	 
	var_dump($array);	 
	var_dump($url_inp);
		
	var_dump($string);
		  }
	  
	  
	  
	  
	  
	  
	  
	  ?>

 

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and here you have the output of the script:

X:mylocation\test-forumpost.php:15:
array (size=36)
  0 => string 'HTTP/1.1 302 Found' (length=18)
  1 => string 'Location: https://www.facebook.com/thisisnothingbutcrap' (length=55)
  2 => string 'Vary: Accept-Encoding' (length=21)
  3 => string 'Content-Type: text/html; charset=UTF-8' (length=38)
  4 => string 'X-FB-Debug: H2nqcWjKt6OFa3H/7fqtn4AmaBe8bs8XU7D8p5iiBbjfIFxKPFk0AXrzmYcsb1j6CQpEAr1WWY+BMO7chtE4vg==' (length=100)
  5 => string 'Date: Thu, 10 Aug 2017 08:20:45 GMT' (length=35)
  6 => string 'Connection: close' (length=17)
  7 => string 'Content-Length: 0' (length=17)
  8 => string 'HTTP/1.1 302 Found' (length=18)
  9 => string 'Location: https://www.facebook.com/unsupportedbrowser' (length=53)
  10 => string 'Strict-Transport-Security: max-age=15552000; preload' (length=52)
  11 => string 'access-control-allow-method: OPTIONS' (length=36)
  12 => string 'Vary: Origin' (length=12)
  13 => string 'Access-Control-Expose-Headers: X-FB-Debug, X-Loader-Length' (length=58)
  14 => string 'Access-Control-Allow-Origin: https://www.facebook.com' (length=53)
  15 => string 'Access-Control-Allow-Credentials: true' (length=38)
  16 => string 'Vary: Accept-Encoding' (length=21)
  17 => string 'Content-Type: text/html; charset=UTF-8' (length=38)
  18 => string 'X-FB-Debug: fc06dn16MiWV1IVm6K5HuEgZBb+X33cGRs/6WG+s8ayq3bhc48K3/4zopvdDa0ikEY97osK2u8Y/OCHRO3eLYQ==' (length=100)
  19 => string 'Date: Thu, 10 Aug 2017 08:20:45 GMT' (length=35)
  20 => string 'Connection: close' (length=17)
  21 => string 'Content-Length: 0' (length=17)
  22 => string 'HTTP/1.1 200 OK' (length=15)
  23 => string 'X-XSS-Protection: 0' (length=19)
  24 => string 'public-key-pins-report-only: max-age=500; pin-sha256="WoiWRyIOVNa9ihaBciRSC7XHjliYS9VwUGOIud4PB18="; pin-sha256="r/mIkG3eEpVdm+u/ko/cwxzOMo1bk4TyHIlByibiA5E="; pin-sha256="q4PO2G2cbkZhZ82+JgmRUyGMoAeozA+BSXVXQWB8XWQ="; report-uri="http://reports.fb.com/hpkp/"' (length=259)
  25 => string 'Pragma: no-cache' (length=16)
  26 => string 'Cache-Control: private, no-cache, no-store, must-revalidate' (length=59)
  27 => string 'X-Frame-Options: DENY' (length=21)
  28 => string 'Strict-Transport-Security: max-age=15552000; preload' (length=52)
  29 => string 'X-Content-Type-Options: nosniff' (length=31)
  30 => string 'Expires: Sat, 01 Jan 2000 00:00:00 GMT' (length=38)
  31 => string 'Vary: Accept-Encoding' (length=21)
  32 => string 'Content-Type: text/html; charset=UTF-8' (length=38)
  33 => string 'X-FB-Debug: 2DMvDPHSjk4qfRmBAJo9RN+YmquJZHNnvnK7JtWUJ5tiz9sFiScne55HgP9PRhnrC/oQQjaPhBiCadng5jtfSg==' (length=100)
  34 => string 'Date: Thu, 10 Aug 2017 08:20:45 GMT' (length=35)
  35 => string 'Connection: close' (length=17)

X:mylocation\test-forumpost.php:16:string 'http://www.facebook.com/thisisnothingbutcrap' (length=44)

X:mylocation\test-forumpost.php:18:string 'HTTP/1.1 302 Found' (length=18)

...........................................................................................

I deliberately input a non existing user and get the output above, similar to a user that does exist. Which of the offsets is used to determine whether it is false or not?

 

Edited by Balderick

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I don't think any header will tell you if a user exists or not.  The original redirect is just because they're redirecting you from http to https.  I wouldn't assume that Facebook will send a header telling you whether or not something exists on their site.

Facebook does have an API, I haven't looked deeply into the capabilities but I would imagine that most things which people need would be supported in their API.

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