The push came after governments in Europe and elsewhere took websites offline as a precaution on Wednesday while website operators scrambled to secure systems running the software.
The emergency shutdowns of banking, airline, rail, tax and government services from Tokyo to Helsinki showed how much public and corporate systems rely on the software, and how hard it is to fix such flaws quickly once they are made public.
"It was a long day and a long night, I know for all the IT and security folks ... I've not seen anything like this in a long, long time," Microsoft CEO Satya Nadella said at a company event in Cologne, Germany, on Thursday.
He said the episode underscored the importance of building digital systems that could be maintained securely.
PHP developers released urgent fixes on Wednesday for vulnerabilities that had lurked in the software for years until they were uncovered using AI, urging users to "update immediately".
As companies and governments deployed patches and suspended websites as a precaution, hacking attempts surged into the millions, according to cloud services firm Cloudflare.
"In the 10 hours before it was publicly announced, across the network we saw thousands of attempts to exploit it," Cloudflare CEO Matthew Prince said in a post on social media X late on Wednesday.
"That jumped to tens of thousands in the 45 minutes post announcement, hundreds of thousands within two hours, and millions now."
Japanese companies including brokerage Nomura, lender Mitsubishi UFJ Financial Group, airline ANA and East Japan Railway said on Thursday they were temporarily suspending some internet services as part of emergency measures.
Insurer Tokio Marine Holdings said it had suspended the website of a group company.
Japan's finance ministry and Meteorological Agency partially suspended online services to implement safety measures, while Japan's National Tax Agency temporarily took down its service.
French telecoms group Orange said it had temporarily suspended access to certain PHP-based websites and applications across several subsidiaries as a precaution.
Tencent Cloud, one of China's largest cloud-computing providers, urged customers to install updated PHP versions but stopped short of calling for widespread website shutdowns.
Finland's state IT services provider Valtori said it had continued installing PHP security patches overnight and was gradually lifting precautionary service blocks after shutting down government public web services a day earlier.
Valtori said the outages were not caused by exploitation of the vulnerabilities or by a cyber-breach, and that it was not aware of any active exploitation of the flaws.
Several Asian governments ordered cybersecurity inspections related to the PHP vulnerabilities on Thursday.
China's industry ministry urged organisations and users to inspect systems immediately and upgrade to the latest secure version of PHP.
It also recommended strengthening cybersecurity monitoring and changing accounts, passwords and keys where necessary.
South Korea raised its private-sector cybersecurity alert level and activated emergency response measures, citing concerns over an increased risk of hacking attacks.
