可以通过命令行运行gnuplot,但不能通过PHP调用吗?

I coded a PHP application that creates charts using gnuplot for specific client applications. It has run well for years.

I’ve just installed gnuplot on new iMac running Mavericks. I used MacPorts to do the install. The install went smoothly. I can access and run gnuplot successfully from the command line in the terminal.

However, when I attempt to run gnuplot via my PHP application, I get the following error:

dyld: Library not loaded: /opt/local/lib/libpng16.16.dylib   Referenced from: /opt/local/bin/gnuplot   Reason: Incompatible library version: gnuplot requires version 26.0.0 or later, but libpng16.16.dylib provides version 19.0.0

There are two things about this that are puzzling me at the moment:

  • Why would gnuplot give no error when called from the command line, but would give this error in response to a PHP call?

  • Macports installed libpng @1.6.9_1. According to the libpng home page (http://www.libpng.org/pub/png/libpng.html), 1.6.9 is the latest version. Why would I get an error saying I need to update libpng?

Does anyone have any thoughts on how I might fix this?

Thanks very much in advance to all for any info!