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.
return_var argument is present, the
return status of the Unix command will be placed here.
If you are going to allow data coming from user input to be passed to this function, then you should be using escapeshellarg() or escapeshellcmd() to make sure that users cannot trick the system into executing arbitrary commands.
Note: If you start a program using this function and want to leave it running in the background, you have to make sure that the output of that program is redirected to a file or some other output stream or else PHP will hang until the execution of the program ends.