json_encode not working in php

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PHP

Apache

Ubuntu

encoding

JSON

In a php web service i need data output as JSON format, am retrieving data from MySQL to array then converting this array to JSON using json_encode. But my result is a empty page, not displaying even any error. If i convert the array using this function 'utf8_encode(array)' its working properly and getting JSON result. This issue is with the new server we configured with os ubundu server 14.0.4, apache2 and php5-5.5.9. Is there any server side settings needed. I have tried with another server with same configuration there its working properly getting JSON result without 'utf8_encode(array)' function in php