php man page for passthru

PASSTHRU(3)								 1							       PASSTHRU(3)

passthru - Execute an external program and display raw output

SYNOPSIS
       void passthru (string  $command, [int  &$return_var])

DESCRIPTION
	The  passthru(3)  function  is	similar  to  the exec(3) function in that it executes a $command. This function should be used in place of
       exec(3) or system(3) 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.

PARAMETERS
	      o $command
		- The command that will be executed.

	      o $return_var
		- If the $return_var argument is present, the return status of the Unix command will be placed here.

RETURN VALUES
	No value is returned.

NOTES
       Warning

	      When allowing user-supplied data to be passed to this function, use escapeshellarg(3) or escapeshellcmd(3) to ensure that users can-
	      not 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.

       Note

	      When safe mode is enabled, you can only execute files within the safe_mode_exec_dir. For practical  reasons,  it	is  currently  not
	      allowed to have .. components in the path to the executable.

       Warning

	      With safe mode enabled, the command string is escaped with escapeshellcmd(3). Thus, echo y | echo x becomes echo y | echo x.

SEE ALSO
       exec(3), system(3), popen(3), escapeshellcmd(3), backtick operator.

PHP Documentation Group 													       PASSTHRU(3)