(PHP 4, PHP 5, PHP 7)passthru — Execute an external program and display raw outputThe passthru() function is similar to theexec() function in that it executes acommand. This functionshould be used in place of exec() orsystem() when the output from the Unix commandis binary data which needs to be passed directly back to thebrowser. A common use for this is to execute something like thepbmplus utilities that can output an image stream directly. Bysetting the Content-type to image/gif andthen calling a pbmplus program to output a gif, you can createPHP scripts that output images directly. The command that will be executed.return_var argument is present, thereturn status of the Unix command will be placed here. No value is returned. 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.