How to parse a JSON string using PHP

Question

I have a JSON string that has 1-n numbers of lat/lng records. It looks something like this:

{\"lat\":37.790388261934424,\"lng\":-122.46047996826172},{\"lat\":37.789608231530124,\"lng\":-122.46344112701416}

What is a good way to parse this to get lat/lng values loop? And do the escaped double quotes impact the parsing?

Thanks, Alex

• ysrb: try json_decode
• lucifurious: Why does it have those slashes in it??
• Dejan Marjanović: Because it is wrapped in double quotes.
• Marc B: @lucifurious: probably because magic_quotes_gpc is turned on.

Answer 1

$ll = '[{"lat":37.790388261934424,"lng":-122.46047996826172},{"lat":37.789608231530124,"lng":-122.46344112701416}]';
$ll = json_decode($ll);
print_r($ll);

Prints...

Array
(
 [0] => stdClass Object
 (
 [lat] => 37.7903882619
 [lng] => -122.460479968
 )
 [1] => stdClass Object
 (
 [lat] => 37.7896082315
 [lng] => -122.463441127
 )
)

• mickmackusa: This answer is missing its education explanation.

Answer 2

Use json_decode.

You will need to unescape quotes first; just use

$unescaped_data = str_replace('\"','"',$data)

• mickmackusa: This is not enough. The input string would still not be valid json after calling str_replace().

Answer 3

In your case it's probably best to use:

$array = json_decode(stripslashes("[$input_string]"), 1);

Note that you will lose some precision on your float values in PHP.

• Genadinik: Is there a way to preserve the precision of the float values in PHP with this operation? They float values are pretty important.
• Dejan Marjanović: If he wrapped it in double quotes, he doesn't need to escape string. His JSON is missing [] around {},{} like you have shown. @Genadinik, 9 decimals is not enough for Lat and Lon?
• mario: @Genadinik: Not with json_decode. And you cannot handle more precise numbers in PHP, it only knows float. The lost precision is minimal, and I actually suspect the Javascript representation is not overly exact either. (A workaround would involve parsing by hand, and using the gmp functions for all coordinates: php.net/manual/en/ref.gmp.php - in your whole application.)
• Salvatore Pannozzo Capodiferro: It works form me, even though the data are inserted into array, so I have to retrieve it using array[0]['data']

Answer 4

JSON_decode and remove escape quotes