About the EXEC function of PHP, what to do with

About the EXEC function of PHP
I wrote the following code in the PHP file:
$cmd = "svn checkout https://..../server/svnconf";
EXEC ($cmd, $results);
I access this page in the browser, without any results,
The command that executes CMD directly on Linux can use, execute this php file with php command also have result output, excuse me what is this? How do you change it?


------Solution--------------------
Explore
I wrote the following code in the PHP file:
$cmd = "svn checkout https://..../server/svnconf";
EXEC ($cmd, $results);
I access this page in the browser, without any results,
The command that executes CMD directly on Linux can use, execute this php file with php command also have result output, excuse me what is this? How do you change it?

------Solution--------------------
Try to start with Apache or Nginx user to know.
------Solution--------------------
Does svn add to $path?

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