<?php
 
$json = '[
	{"nome" : "WallaceMaxters"},
   	{"nome" : "Bigown"},
    {"nome" : "Math", "url" : "http://m...content-available-to-author-only...h.test"}
]';
 
print_r(json_decode($json, TRUE));
 
$convert = json_decode($json, TRUE);
 
array_walk_recursive($convert, function (&$value /** Não esqueça do & **/)
{
	  if (filter_var($value, FILTER_VALIDATE_URL)) return;

      $value = mb_strtoupper($value, 'UTF-8');
});
 
 
print_r($convert);