When you're unsure where a particular executable resides, you can query you YUM installation like so, using
$ repoquery -q --file */phpize
Yum makes use of plugins to enhance it's features. One of these plugins is called fastestmirror. Sometimes this plugin can be the cause of slowness. The mirror sites that this plugin selects can sometimes not be the best ones to use all the time.
You can remove the preferred list of mirrors from this plugin by deleting this file:
$ sudo rm /var/cache/yum/timedhosts.txt
Often times the fastestmirror plugin can cause confusion because some mirror is lagging behind the rest of the mirrors or original site. I'll typically disable it temporarily just to get around the issue like so:
$ sudo yum --disableplugin=fastestmirror install php-devel
$ sudo yum --noplugins install php-devel