documentclass{article}
begin{document}
This is myfile.tex
end{document}

documentclass{article}
usepackage{standalone}
begin{document}
input{source/myfile.tex}
end{document}

This is pdfTeX, Version 3.14159265-2.6-1.40.15 (TeX Live 2014) (preloaded format=latex)
 restricted write18 enabled.
entering extended mode
LaTeX2e <2014/05/01>
Babel <3.9k> and hyphenation patterns for 78 languages loaded.
(./texs/include.tex
(/usr/local/texlive/2014/texmf-dist/tex/latex/base/article.cls
Document Class: article 2007/10/19 v1.4h Standard LaTeX document class
(/usr/local/texlive/2014/texmf-dist/tex/latex/base/size10.clo))
(/usr/local/texlive/2014/texmf-dist/tex/generic/tex4ht/tex4ht.sty)
(/usr/local/texlive/2014/texmf-dist/tex/generic/tex4ht/usepackage.4ht)
(/usr/local/texlive/2014/texmf-dist/tex/latex/standalone/standalone.sty
(/usr/local/texlive/2014/texmf-dist/tex/generic/oberdiek/ifluatex.sty)
(/usr/local/texlive/2014/texmf-dist/tex/generic/oberdiek/ifpdf.sty)
(/usr/local/texlive/2014/texmf-dist/tex/generic/ifxetex/ifxetex.sty)
(/usr/local/texlive/2014/texmf-dist/tex/latex/xkeyval/xkeyval.sty
(/usr/local/texlive/2014/texmf-dist/tex/generic/xkeyval/xkeyval.tex
(/usr/local/texlive/2014/texmf-dist/tex/generic/xkeyval/keyval.tex)))
! Extra else.
l.227     else

?