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.
The command that will be executed.
If the result_code argument is present, the return status of the Unix command will be placed here.
Returns null on success or false on failure.
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.
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.