Original question:

I'm having trouble installing the PHP Pecl Intl extension on my CentOs 5 machine.

After installing both icu and libicu with the following commands:

$ yum install icu
$ yum install libicu

I tried to install the Intl extension like so:

$ /usr/bin/pecl install intl

I selected to search for the default location for the ICU libraries and header files. It ends up crashing like this:

checking whether to enable internationalization support... yes, shared
checking for icu-config... no
checking for location of ICU headers and libraries... not found
configure: error: Unable to detect ICU prefix or no failed. Please verify ICU install prefix and make sure icu-config works.
ERROR: `/tmp/pear/temp/intl/configure --with-icu-dir=DEFAULT' failed

update

After successfully installing the development version of icu as suggested by RusAlex (thanks RusAlex) like so:

$ yum install libicu-devel

I ran into a new problem which I also encountered locally the following command:

$ /usr/bin/pecl install intl

now produces this error:

 /private/tmp/pear/temp/intl/collator/collator_class.c:92: error: duplicate 'static'
 /private/tmp/pear/temp/intl/collator/collator_class.c:96: error: duplicate 'static'
 /private/tmp/pear/temp/intl/collator/collator_class.c:101: error: duplicate 'static'
 /private/tmp/pear/temp/intl/collator/collator_class.c:107: error: duplicate 'static'
 make: *** [collator/collator_class.lo] Error 1
 ERROR: `make' failed

It appears to have something to do with PHP 5.3 being bundled with Intl already. But how can I enable this extension, if I look in my PHP Info than I cannot find any reference to it...