While many big companies use PHP for web application development, some avoid it for the following reasons:
Since PHP was designed for small-scale web applications, it can be challenging for some companies to scale PHP web applications to handle high traffic and a large amount of data.
PHP had some security issues in the past. Hence, some companies prefer using Java and C# in their place as they’re more secure.
PHP is fast but less efficient than other programming languages, especially when handling extensive data and complex architecture.
Some big companies use legacy systems built on older technologies like Java or .NET and may find switching to a new language like PHP challenging.