Why php exec() fails .tex→xelatex→.pdf, but succeed .tex→xelatex→.xdv→xdvipdfmx→.pdf?

Question

The call of command:

$dir = "/path/to/source/file";
exec("cd $dir;xelatex filesource.tex", $output_array[0]);

always fails, but:

$dir = "/path/to/source/file";
exec("cd $dir;/usr/texbin/xelatex -no-pdf filesource.tex", $output_array[0]);// now we have .xdv file
exec("cd $dir;/usr/texbin/xdvipdfmx filesource.xdv", $output_array[1]); 

succeed, and result .pdf file absolutely valid. What is the trick?

Answer 1

In general there are two main cases:

• your LaTeX binaries are known to the system (whichever you might use): This case is pretty simple because you can simply use your first approach without a full path to the binaries.
• your LaTeX binaries are unknown to the system: If you install LaTeX not over repositories (if you're on Linux), but with the TeX Live installer f.i. you'll find them in a location that's unknown to the system. You have to add them to the PATH so that it can be found. The alternative is to use full paths when calling.

You seem to have a system of the second type. So you should either tell PHP to add the LaTeX binary path to PATH or should use full paths when calling.