jsonをphpに変換する方法

　　json_decode ( string $json [, bool $assoc = false [, int $depth = 512 [, int $options = 0 ]]] )

　　$json = '{"a":"php","b":"mysql","c":3}';

<?php   
$json = &#39;{"a":"php","b":"mysql","c":3}&#39;;  
$json_Class=json_decode($json);   
$json_Array=json_decode($json, true);   
print_r($json_Class);   
print_r($json_Array);         
?>

　　stdClass Object (
　　[a] => php
　　[b] => mysql
　　[c] => 3 )
　　Array (
　　[a] => php
　　[b] => mysql
　　[c] => 3 )

echo $json_Class->{'a'};

echo $json_Array['a'];