I encountered this problem today when I installed the PHP extension IMAP in a VPS. When I used the phpize command, I reported an error, so I recorded it to facilitate my search next time. The error message is as shown below. 
 
 Processing process: 
 1. Query the current version 
 rpm -qf /usr/bin/autoconf
 autoconf-2.63-5.1.el6.noarch 
 2. Uninstall the current version and install the new version 
 rpm -e --nodeps autoconf-2.63
 wget http://ftp.gnu.org/gnu/autoconf/autoconf-2.69.tar.gz
 tar -zxvf autoconf-2.69.tar.gz
 cd autoconf-2.69
 mkdir -p /usr/local/autoconf
 ./configure --prefix=/usr/local/autoconf/
 make && make install 
 3. Check the new version and use phpize again. No error message is reported! 
 /usr/local/autoconf/bin/autoconf –V
postid
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