   #PHP Manual Program Execution functions exec proc_close

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                                   passthru

   (PHP 3, PHP 4 )
   passthru --  Execute an external program and display raw output

Description

   void passthru ( 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.

   Warning

   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.

   See also exec(), system(), popen(), escapeshellcmd(), and the backtick
   operator.
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