Fix for php 8.1 compatibility

.gitignore

@@ -166,3 +166,5 @@ pip-log.txt
 
 # Mac crap
 .DS_Store
+
+*.code-workspace

QuickBooks/Cast.php

@@ -255,7 +255,7 @@ static public function cast($type_or_action, $field, $value, $use_abbrevs = true
 			$dh = opendir(dirname(__FILE__) . '/QBXML/Schema/Object');
 			while (false !== ($file = readdir($dh)))
 			{
-				if ($file{0} == '.' or substr($file, -6, 6) != 'Rq.php')
+				if ($file[0] == '.' or substr($file, -6, 6) != 'Rq.php')
 				{
 					continue;
 				}

QuickBooks/Driver/Sql/Mysqli.php

@@ -436,7 +436,7 @@ protected function _escape($str)
 			$str = '';
 		}
 
-		return $this->_conn->real_escape_string($str);
+		return $this->_conn->real_escape_string($str ?? '');
 	}
 
 	/**

QuickBooks/MerchantService/CheckingAccount.php

@@ -55,7 +55,7 @@ public function __construct($routing, $account, $info, $type, $first_name, $last
 
 		$phone = trim(str_replace(array('(', ')', '+', ' ', '.', '-'), '', $phone));
 		if (strlen($phone) == 11 and 
-			$phone{0} == '1')
+			$phone[0] == '1')
 		{
 			$phone = substr($phone, 1);
 		}

QuickBooks/Utilities.php

@@ -92,7 +92,7 @@ static public function mask($message)
 				// It's an XML tag
 				$contents = QuickBooks_Utilities::_extractTagContents(trim($key, '<> '), $message);
 
-				$masked = str_repeat('x', min(strlen($contents), 12)) . substr($contents, 12);
+				$masked = str_repeat('x', min(strlen($contents ?? ''), 12)) . substr($contents ?? '', 12);
 
 				$message = str_replace($key . $contents . '</' . trim($key, '<> ') . '>', $key . $masked . '</' . trim($key, '<> ') . '>', $message);
 			}

QuickBooks/WebConnector/Handlers.php

@@ -544,7 +544,7 @@ public function authenticate($obj)
 		$customauth_wait_before_next_update = null;
 		$customauth_min_run_every_n_seconds = null;
 
-		if (is_array($override_dsn) or strlen($override_dsn)) 	// Custom autj
+		if (is_array($override_dsn) or strlen($override_dsn ?? '')) 	// Custom autj
 		{
 			//if ($auth->authenticate($obj->strUserName, $obj->strPassword, $customauth_company_file, $customauth_wait_before_next_update, $customauth_min_run_every_n_seconds) and
 

QuickBooks/XML.php

@@ -434,7 +434,7 @@ static public function decode($str, $for_qbxml = true)
 			'&' => '&', 		// Make sure that this is *the last* transformation to run, otherwise we end up double-un-encoding things
 			);
 
-		return str_replace(array_keys($transform), array_values($transform), $str);		
+		return str_replace(array_keys($transform), array_values($transform), $str ?? '');
 	}
 }
 

QuickBooks/XML/Backend/Builtin.php

@@ -376,7 +376,7 @@ protected function _parseHelper($xml, &$Root, &$errnum, &$errmsg, $indent = 0)
 				$Node->addAttribute($key, $value);
 			}
 
-			if (false !== strpos($payload, '<'))
+			if (false !== strpos($payload ?? '', '<'))
 			{
 				// The tag contains child tags