Special characters not encoding in the web server

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XML

PHP

conversion

I'm in the process of converting latex to mathml in php.Texmath is the command line tool through which the conversion process can be done.

Latex file:

\mathbf{f} = (f_{1},
f_{2})^{\prime}

test.php:

shell_exec('echo "password" | sudo -S /root/.cabal/bin/texmath latexfile > outputfile');

If I run this php file thorugh command line,it generates the desired output file which is below
command line script:

php test.php

<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
     <mrow>
       <mstyle mathvariant="bold">
         <mi>𝐟</mi>
       </mstyle>
       <mo>=</mo>
       <mo stretchy="false" form="prefix">(</mo>
       <msub>
         <mi>f</mi>
         <mn>1</mn>
       </msub>
       <mo>,</mo>
       <msub>
         <mi>f</mi>
         <mn>2</mn>
       </msub>
       <msup>
         <mo stretchy="false" form="postfix">)</mo>
         <mo>′</mo>
       </msup>
     </mrow>
   </math>

When I run this php file through the browser am getting the output file like

<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
      <mrow>
        <mstyle mathvariant="bold">
          <mi>

It ignores all the mathtype characters. Why is it gives desired output only through the command line not through the browser. When I open these two files in the editor it displays 'UTF-8'. Is this is character encoding issue? How to solve this.

Additional note: If I run php file through local host it gives desired result as the command line php execution does. The problem only with shared web server.