What is PHP, and how did a flaw in its code lead several websites to go dark this week?

PHP is an open-source computer language that powers an estimated 70 per cent of the internet. While websites being taken offline caused alarm, that was done to implement a fix ? which cybersecurity experts say show the system for remedying such issues is working.
Source: What is PHP, and how did a flaw in its code lead several websites to go dark this week? (https://www.cbc.ca/news/business/php-cybersecurity-vulnerability-explainer-9.7392394?cmp=rss)