The project leader and founder of TSPHP (Robert Stoll) is a PHP user who started programming PHP in 2005, becoming involved in several PHP projects before eventually leading PHP projects. Therefore, this has resulted in an awareness of problems surrounding PHP in conjunction with type safety, culminating from the first-hand experience.
Due to this first-hand experience, it was noted, that on many occasions, an undeclared variable or/and type juggling had been the source of a bug. But especially the lack of a good refactoring support within IDEs results in code which rots over the years, because the cost and risk of
refactoring PHP code sometimes merely not pay off. Yet, after being involved in projects that used ASP.NET C#, a type-safe programming language, the founder became enabled to visualise opportunities for TSPHP.
Additionally, the founder argues that TSPHP would provide vast improvements towards better code quality and to the maturity of PHP itself. It would result in faster development and more robust web applications, since IDE's are able to better support the programmers and type safety allows for the discovery of certain bugs during compile time automatically. Moreover, the step of compiling source code enables further features such as code optimisation during compile time (PHP makes already some optimisations but at runtime), real support for AOP and other new language concepts including enums, named parameters, operator overloading etc.
To conclude, the whole PHP community could benefit from this project and this is the main reason why the founder of this project develops and publishes this project under a permissive open source license/BSD-style license, namely under Apache License 2.0.