get object key ending in highest number but not numerical - php

Question

I have an stdclass object like this:
{
"type": "photo",
"photo": {
"id": id,
"album_id": album_id,
"owner_id": owner_id,
"photo_75": "https://example.com/random_unique_string/random_unique_name.jpg",
"photo_130": "https://example.com/random_unique_string/random_unique_name.jpg",
"photo_604": "https://example.com/random_unique_string/random_unique_name.jpg",
"photo_807": "https://example.com/random_unique_string/random_unique_name.jpg",
"photo_1280": "https://example.com/random_unique_string/random_unique_name.jpg",
"photo_2560": "https://example.com/random_unique_string/random_unique_name.jpg",
"width": 2560,
"height": 1440,
"text": "",
"date": 1517775329,
"access_key": "key"
}
The more complete look is on this pic:
I have my code structure like this:
foreach ( $response->posts as $key => $element ) {
if ( isset ($element->attachments) ) {
foreach ( $element->attachments as $key_att => $attachment ) {
if ( $attachment->type == 'photo' ) {
//get the value of the photo with the maximum resolution
}
}
}
}
How do I get only the value of photo_2560 in this case, pointing it to the photo_ ending with the maximum numeric value? max only works with completely numeric keys... Perhaps would need a regex, but I'm weak at that. Thanks for the help.
P. S. I asked about an array and not an object initially, so the answers given are valid, I made a mistake myself. The initial name of the question was get array key ending in highest number but not numerical. I then edited it to reflect my specific issue. Sorry about the confusion.

Answer 1

Here is what I would do using the little known preg_grep function:
$array = [
"photo_75"=> "https=>//example.com/random_unique_string/random_unique_name.jpg",
"photo_130"=> "https=>//example.com/random_unique_string/random_unique_name.jpg",
"photo_604"=> "https=>//example.com/random_unique_string/random_unique_name.jpg",
"photo_807"=> "https=>//example.com/random_unique_string/random_unique_name.jpg",
"photo_1280"=> "https=>//example.com/random_unique_string/random_unique_name.jpg",
"photo_2560"=> "https=>//example.com/random_unique_string/random_unique_name.jpg",
"width"=> 2560,
"height"=> 1440,
"text"=> "",
"date"=> 1517775329,
"access_key"=> "key"
];
$array = preg_grep('/^photo_\d+$/', array_keys($array));
sort($array, SORT_NATURAL);
print_r(end($array));
Output
photo_2560
Sandbox
Preg Grep lets you search an array using a regular expression, It's sort of like using array filter and preg_match
$array = array_filter($array, function($item){
return preg_match('/^photo_\d+$/', $item);
});
But obviously much shorter. Like array filter it's mostly for use against the values and not the keys, but we can use array_keys to get around this. Array Keys returns an array of the keys as the new arrays value array(0=>'key', ..) which is exactly what we want.
UPDATE
Based on this comment:
Is there an alternative of array_keys for an object? Because I confused it with an array, unfortunately.
No but you can cast it (array)$obj to an array if the properties are public. We can demonstrate this easily:
class foo{
public $bar = 'hello';
}
print_r(array_keys((array)(new foo)));
Output
array(
0 => 'bar' //which is the key 'bar' or the property named $bar
)
Sandbox
While it's not "ideal" it will work.
UPDATE1
I made edits to my question, please take a look. I don't understand how to apply your example in this case :(
I think it's $attachment->photo in your code, it's really hard to tell in the image. It's whereever the 'stuff' at the very top of you question came from, your example data.
In anycase with your code you would do something like this:
foreach ( $response->posts as $key => $element ) {
if ( isset ($element->attachments) ) {
foreach ( $element->attachments as $key_att => $attachment ) {
if ( $attachment->type == 'photo' ) {
//new code
$array = preg_grep('/^photo_\d+$/', array_keys((array)$attachment->photo));
sort($array, SORT_NATURAL);
$result = end($array);
print_r($result);
}
} //end foreach
}
}//end foreach
By the way the Regex I am using ^photo_\d+$ is basically this
^ match the start of the string
photo_ match "photo_" litterally
\d+ match one or more digits
$ match the end of the string.
Note the ^ can have different meaning depending where it is, for example if its in a character class [0-9] (A range of characters 0 to 9 same as \d) like this [^0-9] it means NOT so it makes the character class match everything but what is in it. Or "negation". Which is a bit confusing, but that is how it works. In this case it would be anything NOT a digit.
By using the ^ and $ we are saying that our Regex must match the whole string. So we can avoid things like somephoto_79890_aab which if we didn't have the start and end markers our Regex photo_\d+ would match this part some[photo_79890]_aab.
Cheers.

Answer 2

Regex won't tell you what the highest number is. But, these "photo_N" keys can be sorted using natural order.
You didn't mention the name of your variable, so I'll just assume $array here for the sake of convenience.
Let's first get only the "photo_N" elements from the array:
$photos = array_filter(
$array['photo'],
function($key) {
return substr($key, 0, 6) === "photo_";
},
ARRAY_FILTER_USE_KEY
);
We can now sort the result of that by key, using natural order:
ksort($photos, SORT_NATURAL);
This should have put the photo with the highest numerical key at the end, so you can get its value using:
$photo = end($photos);