我收到此错误。您能帮我理解为什么会来吗，这意味着什么。我没有更改任何代码。它运行在PHP 7.1上，操作系统是Linux。
PHP Warning: PHP Startup: SourceGuardian: Unable to initialize module
Module compiled with module API=20160303
PHP compiled with module API=20170718
These options need to match in Unknown on line 0
PHP Fatal error: Uncaught Error: Call to undefined function
simplexml_load_string() in public_html/lib/Varien/Simplexml/Config.php:510
Stack trace:
#0 /home3/ramesqj3/public_html/lib/Varien/Simplexml/Config.php(498):
Varien_Simplexml_Config->loadString('<?xml version="...',
'Mage_Core_Model...')
#1/home3/ramesqj3/public_html/app/code/core/Mage/Core/Model/Config.php(277):
Varien_Simplexml_Config->loadFile('/home3/ramesqj3...')
#2 /home3/ramesqj3/public_html/app/code/core/Mage/Core/Model/App.php(391):
Mage_Core_Model_Config->loadBase()
#3 /home3/ramesqj3/public_html/app/code/core/Mage/Core/Model/App.php(304):
Mage_Core_Model_App->_initBaseConfig()
#4 /home3/ramesqj3/public_html/app/code/core/Mage/Core/Model/App.php(348):
Mage_Core_Model_App->baseInit(Array)
#5 /home3/ramesqj3/public_html/app/Mage.php(686): Mage_Core_Model_App-
>run(Array)
#6 /home3/ramesqj3/public_html/index.php(83): Mage::run('', 'store')
#7 {main}
thrown in public_html/lib/Varien/Simplexml/Config.php on line 510