While it is not recommended to use PHP version 5.6.40, as it has known vulnerabilities, you can still use it if you apply the necessary security patches and take additional security measures.
If you are running PHP 5.6.40, you are likely failing major security compliance standards. php version 5640 vulnerabilities verified
Never use == for security checks. Always use === (strict comparison). While it is not recommended to use PHP version 5
PHP 5.6.40 is significantly slower and consumes far more memory than modern equivalents. PHP 8.x versions can process up to three times as many requests per second while drastically lowering infrastructure hosting costs. Remediation and Mitigation Strategies Always use === (strict comparison)
Multiple flaws in the mbstring and PHAR extensions can cause memory corruption, potentially leading to full system compromise.
Running an EOL runtime environment introduces compounding security risks. For PHP 5.6.40, these risks fall into two distinct categories: