<?php

$string = "txn_status=0|txn_msg=success|txn_err_msg=NA|clnt_txn_ref=969239|tpsl_bank_cd=470|tpsl_txn_id=192630337|txn_amt=1.00|clnt_rqst_meta={itc:NIC~TXN0001~122333~rt14154~8 mar 2014~Payment~forpayment}{custname:test}|tpsl_txn_time=26-12-2015 15:56:20|tpsl_rfnd_id=NA|bal_amt=NA|rqst_token=hdfs-df-jkfhskjfhsjkd|hash=jhdsfs54367jhf";

preg_match_all("/([^|]+)=([^|]+)/", $string, $array);

$output = array_combine($array[1], $array[2]);

echo json_encode($output, JSON_PRETTY_PRINT);