[CentOS] pecl install json on CentOS 5.8

Hi

Any clue about the below issue?

/usr/bin/pecl install json
WARNING: channel "pear.php.net" has updated its protocols, use
"channel-update pear.php.net" to update
downloading json-1.2.1.tgz ...
Starting to download json-1.2.1.tgz (17,780 bytes)
......done: 17,780 bytes
11 source files, building
running: phpize
Configuring for:
PHP Api Version:         20041225
Zend Module Api No:      20050922
Zend Extension Api No:   220051025
/usr/bin/phpize: /tmp/tmpJaaJaV/json-1.2.1/build/shtool: /bin/sh: bad
interpreter: Permission denied
Cannot find autoconf. Please check your autoconf installation and the
$PHP_AUTOCONF
environment variable is set correctly and then rerun this script.

ERROR: `phpize' failed
[root at bom-bott ~]# ll /bin/sh
lrwxrwxrwx 1 root root 4 Mar 30 12:50 /bin/sh -> bash
[root at bom-bott ~]# echo PHP_AUTOCONF
PHP_AUTOCONF
[root at bom-bi1 ~]# echo $PHP_AUTOCONF
/usr/bin/autoconf
[root at bom-bott ~]# whereis autoconf
autoconf: /usr/bin/autoconf /usr/local/bin/autoconf
/usr/share/autoconf /usr/share/man/man1/autoconf.1.gz
[root at bom-bott ~]# /usr/bin/pecl install json
[root at bom-bott ~]# whereis phpize
phpize: /usr/bin/phpize /usr/share/man/man1/phpize.1.gz