Phpstan hasn't identified any errors in Samples in a long time. But, as it turns out, one particular error is suppressed:
```
Variable $helper might not be defined.
```
This error would be generated by almost all samples, and the errors that it suppresses will become problematic if we move to Level 10. We are not yet committed to doing that, but it is pretty easy to write a script to change the samples so that error no longer happens, and there isn't really any reason to delay doing so. The results of that script constitute this PR.
* Validate Post Item in Convert-Online.php
* Correct Samples - Currency, Accounting, and Downloader
* Smarter Color Formatting for Currency
* Use helper->log Rather than echo in Convert-Online
Responding to comment from @PowerKiki about use of echo for error messages. I do not believe that an exception is warranted, but other scripts use helper->log for error messages, and now so will this one.
The samples have become unwieldy when running them from a browser. In particular, the drop-down lists are fixed size with no scrolling, and many of them are now just too large. I have moved all the Calculation samples up a level, and broken several categories (Basic, Chart, DateTime, Engineering, Financial, and Reader) into several pieces.
Convert-Online (now found in the Engineering category) had a number of different problems which are now resolved. It is the only member with any significant code change.
oleibman