patch php generator

[AxiosLeo]

1. Supported emit test files.
2. Optimizing the ResolveImports method.
3. Optimizing test case.
4. Optimizing emit @throw comment.

[codecov-commenter]

Codecov Report

Merging #17 into master will decrease coverage by 0.20%.
The diff coverage is 72.72%.

@@            Coverage Diff             @@
##           master      #17      +/-   ##
==========================================
- Coverage   95.29%   95.09%   -0.21%     
==========================================
  Files          15       15              
  Lines        2041     2079      +38     
==========================================
+ Hits         1945     1977      +32     
- Misses         96      102       +6     

Impacted Files	Coverage Δ
src/resolver/base.js	94.91% <ø> (+6.54%)	⬆️
src/langs/php/combinator.js	89.37% <43.33%> (-1.86%)	⬇️
src/langs/php/package_info.js	65.95% <55.55%> (-2.34%)	⬇️
src/generator.js	91.57% <100.00%> (+0.08%)	⬆️
src/langs/common/items.js	100.00% <100.00%> (ø)
src/resolver/client.js	100.00% <100.00%> (+0.55%)	⬆️
src/langs/common/combinator.js	100.00% <0.00%> (+2.12%)	⬆️

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