Php function issues

[brett-sargeant]

The drupal based platform we use to host our websites has found these issues with the IMu php code.
(I've removed the reference to the site name in the paths)

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Line lib/IMu/MIME.php

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75 Undefined variable: $file
177 Access to an undefined property IMuMIMEType::$type.

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Line lib/IMu/Stream.php

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483 Access to an undefined static property IMuStream::$blockSize.

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Line lib/IMu/Trace.php

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170 Should not use function "debug_backtrace", please change the code.
215 Should not use function "print_r", please change the code.

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Line lib/IMu/Web/Platform.php

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150 Access to an undefined property IMuWebPlatform::$device_mobile.
151 Access to an undefined property IMuWebPlatform::$device_phone.

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