ok problem solve
my server is running centos and the json library is nost installed
i was following this
Installing JSON on CentOS 5.4
I’ve been toying around with ExtJS for the past few days and wanted to start using JSON to insert data into my widgets. To my surprise (or lack thereof) CentOS does not include the JSON library with any of the default installed binaries. Below is how to go about installing JSON support for php:
Update PHP
yum update php
Install the PHP development package
yum install php-devel
Install pear for php
yum install php-pear
Use pecl (from pear installation) to buildinstall JSON
pecl install json
Create json.ini for your php installation
echo "extension=json.so" > /etc/php.d/json.ini
Reload Apache
service httpd restart
At this point, if you see the below when you look at the output of phpino(); you have successfully installed json.