PhP howto sizeof(JSON:array[]) - php

Question

I have a bug in my code but the solution is buried deep in a JSON return
https://api.instagram.com/v1/users/self/media/liked?access_token=207436640.c57b856.b0a8944d1e0c4e70a6ec581679c656b5
There are array[17] I must loop through
foreach ($arr['data'][0]['likes']['data'] as $liker){
echo '<img src="'.$liker['profile_picture'].'" /></br>';
echo '<p> '.$liker['username'].'</p></br>';
}
Works fine for one, but
for($i = 0; $i < sizeof($arr['data'][]); $i++){
echo '<img src="'.$arr['likes']['data']['profile_picture'].'" /></br>';
echo '<p> '.$liker['username'].'</p></br>';
}
has less than desirable results.
Fatal error: Cannot use [] for reading in /var/www/localhost/htdocs/instagram2.php on line 68
or if I remove the [], I get 'undefined 'likes'.
How do I properly loop through a JSON subarray?

Answer 1

You way of approaching the for compared to the foreach is wrong. In the foreach the current item during the iteration is automatically assigned to $liker, however nothing like this occurs in the for. You are only incrementing the value of $i.
/// #shaddy has said, this is the correct way to access the array size
/// it is more optimal to calculate it outside of the loop.
$len = sizeof($arr['data']);
/// with a for loop, you have to use $i to calculate the item
for($i = 0; $i < $len; $i++){
$item = $arr['data'][$i];
/// and then access each of the subitems inside $item
...
}
But you also have other problems. You are seemingly trying to output the image of each of the profile_pictures for the likers; but this is also an array of data. In your first example you are directly stepping through this array, so everything works. In your second however you are only looping the container array, and not the list of likers. To get this to work you must have a second loop:
$len = sizeof($arr['data']);
/// with a for loop, you have to use $i to calculate the item
for($i = 0; $i < $len; $i++){
$item = $arr['data'][$i];
/// best to check for existence before accessing to avoid errors
if ( !empty($item['likes']['data']) ) {
$likers = $item['likes']['data'];
$len2 = sizeof($likers);
/// step each of the likers
for($k = 0; $k < $len2; $k++){
$liker = $likers[$k];
if ( !empty($liker['profile_picture']) ) {
echo '<img src="'.$liker['profile_picture'].'" /></br>';
}
/// the username field is also part of the user array inside item
if ( !empty($liker['username']) ) {
echo '<p> '.$liker['username'].'</p></br>';
}
}
}
}
However the above all looks quite complicated, I usually don't use for loops in php, foreach has a much nicer interface to work with, and is designed to work with arrays:
foreach ( $arr['data'] as $i => $item ) {
if ( !empty($item['likes']['data']) ) {
foreach ( $item['likes']['data'] as $k => $liker ) {
if ( !empty($liker['profile_picture']) ) {
echo '<img src="' . $liker['profile_picture'] . '" /></br>';
}
if ( !empty($liker['username']) ) {
echo '<p> ' . $liker['username'] . '</p></br>';
}
}
}
}
Of course you may just have been wanting to loop through the likers array just like in your first example, to do that with a for you just need:
$likers = $arr['data'][0]['likes']['data'];
$len = sizeof($likers);
for( $i = 0; $i < $len; $i++ ){
echo '<img src="' . $likers[$i]['profile_picture'] . '" /></br>';
echo '<p> ' $likers[$i]['username'] . '</p></br>';
}
please note:
There is also another caveat to be aware of, and this will cause some of the above snippets to fail if it is not true. All the above code is always working with arrays, and so the $arr array must only contain arrays. However your dataset shows a mixture of arrays and objects. When dealing with objects in PHP you need to use a different accessor.
As I am unable to see how you are loading your JSON it is difficult to advise, as depending on the manner objects can be converted into arrays. All your examples have been treating every part of your structure as an array, and that is why I have assumed the same in the above.
However the standard way would be to use json_decode which would/should preserve the array/object difference by default. This means where ever there is an object you will need to use $obj -> prop rather than $obj['prop'], so my preferred example above would look like this:
foreach ( $arr['data'] as $i => $item ) {
if ( !empty($item->likes['data']) ) {
foreach ( $item->likes['data'] as $k => $liker ) {
if ( !empty($liker->profile_picture) ) {
echo '<img src="' . $liker->profile_picture . '" /></br>';
}
if ( !empty($liker->username) ) {
echo '<p> ' . $liker->username . '</p></br>';
}
}
}
}
Also if you prefer working just with arrays, you could use something like this:
https://coderwall.com/p/8mmicq/php-convert-mixed-array-objects-recursively

Answer 2

Well $arr['data'][] is invalid way to reference the data value of the array the correct one is $arr['data']
for($i = 0; $i < sizeof($arr['data']); $i++){
foreach ($arr['data'][$i]['likes']['data'] as $liker) {
echo '<img src="'.$liker['profile_picture'].'" /></br>';
echo '<p> '.$liker['username'].'</p></br>';
}
}
You can read more about arrays here http://php.net/manual/en/language.types.array.php .