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Fatal error: Uncaught Error: Call to undefined function Facebook\PseudoRandomString\mb_substr() in /home/web/main/Facebook/PseudoRandomString/PseudoRandomStringGeneratorTrait.php:56 Stack trace: #0 /home/web/main/Facebook/PseudoRandomString/OpenSslPseudoRandomStringGenerator.php(65): Facebook\PseudoRandomString\OpenSslPseudoRandomStringGenerator->binToHex('\x11w\xF5I\xF4v\x9D\xC0H\xA9\xAE\xC2\xEDI7...', 32) #1 /home/web/main/Facebook/Helpers/FacebookRedirectLoginHelper.php(153): Facebook\PseudoRandomString\OpenSslPseudoRandomStringGenerator->getPseudoRandomString(32) #2 /home/web/main/Facebook/Helpers/FacebookRedirectLoginHelper.php(170): Facebook\Helpers\FacebookRedirectLoginHelper->makeUrl('https://bullfan...', Array, Array, '&') #3 /home/web/v1/page/main/login.php(8): Facebook\Helpers\FacebookRedirectLoginHelper->getLoginUrl('https://bullfan...', Array) #4 /home/web/v1/html.php(104): require_once('/home/web/v1/pa...') #5 /home/web/v1/main.php(182): require_once('/home/web/v1/ht...') #6 /home/web/main/main.php(109): req in /home/web/main/Facebook/PseudoRandomString/PseudoRandomStringGeneratorTrait.php on line 56