How to sort json string by a key value before loop?

Question

I would like to sort this kind of json string by itemCategory_title or itemCategory_id before the loop? i tried to use usort but it didn't sort!

could any one tell me how this can be done ?

json string sample data:

{ '5123': {
            'tmp': '1', 'name': 'mango', 'abc': 'abcd4 http://mysite/items/1234', 'number': '1123', 'itemCategory_title': 'fruits', 'logo': '2123.png', 'itemCategory_id': '90'
        }, '700': {
            'tmp': '0', 'name': 'cherry', 'abc': 'abcd4 http://mysite/items/1235', 'number': '1124', 'itemCategory_title': 'fruits', 'logo': '2124.png', 'itemCategory_id': '91'
        } }

php code:

$code2 = stripslashes($_POST['outputtext']);

$clean_str = str_replace("p '","'",$code2);
$clean_str = str_replace('\'', '"', $clean_str);

$data = json_decode($clean_str, true);

//here i want to sort $data by itemCategory_title or itemCategory_id

usort($data, function($a, $b) { //Sort the array using a user defined function
    return $a->itemCategory_id > $b->itemCategory_id ? -1 : 1; //Compare the scores
}); 

foreach( $data as $item ) {
  echo $item['tmp'];
  echo $item['name'];
  echo $item['abc'];
  echo $item['number'];
  echo $item['itemCategory_title'];
  echo $item['log'];
  echo $item['itemCategory_id'];    

?>
<a href="./process.php?tmp=<?php  echo $item['tmp'] ; ?>&name=<?php  echo $item['name']; ?>&abc=<?php  echo $item['abc'] ; ?>&itemCategory_title=<?php  echo $item['itemCategory_title'] ; ?>&log=<?php  echo $item['log'] ; ?>&itemCategory_id=<?php  echo $item['itemCategory_id'] ; ?>"><?php  echo $item['itemCategory_title'] ; ?> </a> <br />
<?

}

?>

Can i ask you why you want to sort a string representation of an object? — x13
– x13, Commented Nov 19, 2015 at 23:48
@ThisNameBetterBeAvailable He's sorting it after he decodes it into an associative array. — Barmar
– Barmar, Commented Nov 19, 2015 at 23:49
@Barmar but why is he sorting it (don't say object nor array)? — x13
– x13, Commented Nov 19, 2015 at 23:53
He wants the HTML to show them in the order of itemCategory_id. — Barmar
– Barmar, Commented Nov 19, 2015 at 23:54
Why don't you print_r($data) after your json_decode? You'll see your problem. — StackSlave
– StackSlave, Commented Nov 19, 2015 at 23:55

Barmar · Accepted Answer · 2015-11-20 00:46:08Z

3

In the usort function, ->itemCategory_id should be ['itemCategory_id']. Since you gave the second argument to json_decode(), the JSON objects become PHP associative arrays, not objects.

If you'd turned on error reporting you would have seen the notices about trying to get the properties of a non-object. You got it right when you were echoing them in the foreach loop, but not the usort comparison function.

usort($data, function($a, $b) { //Sort the array using a user defined function
    return $a['itemCategory_id'] > $b['itemCategory_id'] ? -1 : 1; //Compare the scores
});

To sort by name within categories, it should be:

usort($data, function($a, $b) { //Sort the array using a user defined function
  if ($a['itemCategory_id'] == $b['itemCategory_id']) {
    return $a['name'] > $b['name'] ? 1 : -1;
  } else {
    return $b['itemCategory_id'] - $a['itemCategory_id'];
  }
});

This sorts category IDs descending, and names ascending.

edited Nov 20, 2015 at 0:46

answered Nov 19, 2015 at 23:53

Barmar

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13 Comments

Christophe Willemsen Over a year ago

Note that the ternary operation is not mandatory, just use return $a['itemCategory_id'] - $b['itemCategory_id'] for ASC order and switch $a and $b for DESC order.

Barmar Over a year ago

@ChristopheWillemsen That works in this case because they're numbers, it wouldn't work in the more general case. And it's not really relevant to the problem in the code.

user1788736 Over a year ago

Thanks all for replies.Barmar it sorted correctly now. If i want to sort all items that got same itemCategory_id alphabetically do i need to push those items with same itemCategory_id to another array then sort ? or is there any easier method ?

Barmar Over a year ago

You add a check for that to the usort function. if ($a['itemCategory_id'] == $b['itemCategory_id']) { return $a['name'] > $b['name'] ? -1 : 1; } else { ... }`

user1788736 Over a year ago

i tried that but didn't sort it the way i want it. This is the way i want my final data be sorted:apple (fruits=>itemCategory_id=12) bannana(fruits=>itemCategory_id=12) bmw(cars=>itemCategory_id=11) ford(cars=>itemCategory_id=11) i want all items that have same itemcategory for example id=11 be sort a-z not mixed or z-a

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