json_decode() returns string type?

Hi,
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I'm passing a JSON-encoded string to json_decode() and am expecting
its output to be an object type, but am getting a string type instead.
How can I return an object?
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In the docs, the following returns an object:
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$json = '{"a":1,"b":2,"c":3,"d":4,"e":5}';
var_dump(json_decode($json));
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However, if I json_encode() the string first and then call
json_decode(), the output is a string and not an object:
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$json = json_encode('{"a":1,"b":2,"c":3,"d":4,"e":5}');
var_dump(json_decode($json));
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This is just a simplified example--in practice what I'm doing is
pushing a JSON-encoded string to PHP via AJAX (or at least "AJ" ;).
However it does illustrate the problem of converting this encoded JSON
string to an object I can read in PHP (e.g., "$json->a").
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How can I return an object type?
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Thanks!
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