How to parse the post_meta data in json using php?

I am trying to parse the meta value of post in wordpress db using unserialize function but it returns an error like follows

  <br />
  <b>Notice</b>:  unserialize() [<a href='function.unserialize'>function.unserialize</a>]: Error at offset 562 of 2954 bytes in <b>/home/shyampri/public_html/http://ift.tt/1yMWng9; on line  <b>45</b><br />