PHP Threading and global variables

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  • Pat A
    #1

    PHP Threading and global variables

    Are global variables thread safe? We are seeing competing threads
    modifying global variables on calls to the same page. We are running in
    ISAPI mode. Are globals protected internally inside of the PHP runtime
    with a semaphore or some other mechanism?

    Tags: None
    • Pat A
      #2
      Re: PHP Threading and global variables


      By the way, we are only seeing this on a multi-processor machine.

        Comment

        • Chung Leong
          #3
          Re: PHP Threading and global variables

          "Pat A" <pwalessi1@hotm ail.com> wrote in message
          news:1107544624 .483219.212310@ f14g2000cwb.goo glegroups.com.. .[color=blue]
          > Are global variables thread safe? We are seeing competing threads
          > modifying global variables on calls to the same page. We are running in
          > ISAPI mode. Are globals protected internally inside of the PHP runtime
          > with a semaphore or some other mechanism?
          >[/color]

          Yes. They managed, along with all internal data, by TSRM, the PHP
          thread-safe resource manager. Based on the id of current thread, a block of
          memory is obtained/allocated by TSRM. The thread data registry itself is
          protected by a mutex.

          The behavior you described is rather odd. As far as I know, there is no
          thread-unsafe version of the PHP engine for Windows.

          Can you show us some code sample?


            Comment

            • Pat A
              #4
              Re: PHP Threading and global variables

              We're seeing the problem in the free FPDF library. We have a php page
              that instantiates the FPDF class multiple times in a loop. The
              instances of FPDF seem to be stepping on each other.

                Comment

                • Chung Leong
                  #5
                  Re: PHP Threading and global variables


                  "Pat A" <pwalessi1@gmai l.com> wrote in message
                  news:1108585109 .304104.42140@g 14g2000cwa.goog legroups.com...[color=blue]
                  > We're seeing the problem in the free FPDF library. We have a php page
                  > that instantiates the FPDF class multiple times in a loop. The
                  > instances of FPDF seem to be stepping on each other.
                  >[/color]

                  Unfortunately, not all PHP extension are threadsafe. You might want to
                  contact the people who wrote FPDF.


                    Comment

                    • noSpam
                      #6
                      Re: PHP Threading and global variables

                      Chung Leong wrote:[color=blue]
                      > "Pat A" <pwalessi1@gmai l.com> wrote in message
                      > news:1108585109 .304104.42140@g 14g2000cwa.goog legroups.com...
                      >[color=green]
                      >>We're seeing the problem in the free FPDF library. We have a php page
                      >>that instantiates the FPDF class multiple times in a loop. The
                      >>instances of FPDF seem to be stepping on each other.
                      >>[/color]
                      >
                      >
                      > Unfortunately, not all PHP extension are threadsafe. You might want to
                      > contact the people who wrote FPDF.
                      >
                      >[/color]
                      Don't rely upon PHP being thread safe, the problem doesn't lie
                      neccesarily with PHP, its the libraries PHP employs that may - read are
                      not - thread safe. Assume that any PHP program is running in a thread
                      unsafe environment - better safe than sory <g>

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