Description:
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As described on http://www.php.net/manual/en/ref.dio.php i added --enable-dio as option, my complete configuration command is:

./configure --with-apxs2=/usr/sbin/apxs2-prefork --with-mysql --with-gd --enable-gd-native-ttf --with-zlib-dir=/usr/lib --with-png-dir=/usr/lib --with-jpeg-dir=/usr/lib --with-freetype-dir=/usr/lib --with-bz2 --enable-dio 

Works fine, but at the end of the output, I get:
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Thank you for using PHP.

Notice: Following unknown configure options were used:

--enable-dio

Check './configure --help' for available options

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So, option --enable-dio is not recognized. With 

./configure --help | grep dio

i also get no result. After 'make install', calling the function dio_open() then calls an fatal error (unknown function...).