(PHP 4, PHP 5, PHP 7, PHP 8)
passthru — Execute an external program and display raw output
$command, int &$result_code = null): ?bool
   The passthru() function is similar to the
   exec() function in that it executes a
   command. This function
   should be used in place of exec() or
   system() when the output from the Unix command
   is binary data which needs to be passed directly back to the
   browser.  A common use for this is to execute something like the
   pbmplus utilities that can output an image stream directly.  By
   setting the Content-type to image/gif and
   then calling a pbmplus program to output a gif, you can create
   PHP scripts that output images directly.
  
commandThe command that will be executed.
result_code
       If the result_code argument is present, the 
       return status of the Unix command will be placed here.
      
No value is returned.
When allowing user-supplied data to be passed to this function, use escapeshellarg() or escapeshellcmd() to ensure that users cannot trick the system into executing arbitrary commands.
Note:
If a program is started with this function, in order for it to continue running in the background, the output of the program must be redirected to a file or another output stream. Failing to do so will cause PHP to hang until the execution of the program ends.