Inserting wrong data in table wordpress

When I insert the serialize data in the postmeta table the data is modified while inserting like:

s:107:"a:4:{s:6:"page_1";s:5:"third";s:6:"page_2";s:5:"first";s:6:"page_3";s:6:"fourth";s:6:"page_4";s:5:"fifth";}";

but when I print this data before inserting it is displaying this that is right:

a:4:{s:6:"page_1";s:5:"third";s:6:"page_2";s:5:"first";s:6:"page_3";s:6:"fourth";s:6:"page_4";s:5:"fifth";}

while inserting it is automatically add s:107:" in front of data or "; in back of data.

Can any one please tell me why it is inserting like this.

Thanks in Advance

via Chebli Mohamed