- array_push: documentation ( source)
- json_decode: documentation ( source)
- json_encode: documentation ( source)
<?php
$comp = '[{"date":"2014-10-04","day:"mon"},{"date":"2014-10-03","day":"tue"}]';
$arr1 = array('date' => '2015-10-04' , 'day' => 'wed');
array_push(json_decode($comp,true),$arr1);
echo json_encode($comp);