( string command [, int return_var])
The passthru() function is similar to the
exec() function in that it executes a
command. If the
return_var argument is present, the return
status of the Unix command will be placed here. 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.
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
注: 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.
safe mode is enabled, you can only
execute executables within the safe_mode_exec_dir.
For practical reasons it is currently not allowed to have ..
components in the path to the executable.
With safe mode enabled,
all words following the initial command string are treated as a single argument. Thus,
echo y | echo x becomes echo "y | echo x".
See also exec(), system(),
and the backtick