Undefined index error referencing PHP array - php

Question

I'm getting an error whilst trying to iterate some data and I can't figure out what I'm doing wrong. This is the format of the data I have returned from an API request:
Array
(
[search-results] => Array
(
[entry] => Array
(
[0] => Array
(
[author] => Array
(
[0] => Array
(
[authname] => Griffin J.
[surname] => Griffin
[initials] => J.M.
)
[1] => Array
(
[authname] => Williams D.
[surname] => Williams
[initials] => D.H.
)
)
)
[1] => Array
( ...etc...
)
)
)
)
For reference the above data printout is from $eachJson in the code below.
I can only do an API request to get 100 results at a time, so I set up a for loop to perform the search 100 times, then next 100 etc. As there are multiple authors per record, I set up a foreach loop to iterate the authors and this is where I'm getting the error messages:
Notice: Undefined index: author in C:\xampp\htdocs\academic_intelligence\public\ScopusTest.php on line 42
Warning: Invalid argument supplied for foreach() in C:\xampp\htdocs\academic_intelligence\public\ScopusTest.php on line 42
Here's the code:
$apiKey = "&apiKey=c2cb86c3a511ed34dd6f03f481c637c1";
$search1 = urlencode("badgers");
$search2 = urlencode(" OR weasels");
$start = 0;
$scopusData = [];
// create an array to represent citation values to ignore, i.e. not interested
// in any publications with less than 4 citations
$ignore = array(0, 1, 2, 3);
// set processing time for browser before timeout
ini_set('max_execution_time', 3600);
// override default PHP memory limit
ini_set('memory_limit', '-1');
// REST HTTP GET Request searching for people associated with keywords (term)
$searchLink = "http://api.elsevier.com/content/search/scopus?query=KEY(" . $search1 . $search2 . ")" . $apiKey . "&sort=citedby-count&count=100&start=" . $start . "&view=complete";
// save results to a variable
$searchResponse = file_get_contents($searchLink);
// convert JSON to PHP variable
$searchJson = json_decode($searchResponse, true);
// get total number of results for query to know when to stop iterating data
$total = $searchJson['search-results']['opensearch:totalResults'];
// iterate data loading next 200 results (max) each time and adding new results to array
for ($i = $start; $i <= $total; $i+=100) {
// REST HTTP GET Request searching for people associated with keywords (term)
$eachLink = "http://api.elsevier.com/content/search/scopus?query=KEY(" . $search1 . $search2 . ")" . $apiKey . "&sort=citedby-count&count=100&start=" . $i . "&view=complete";
// save results to a variable
$eachResponse = file_get_contents($eachLink);
$eachJson = json_decode($eachResponse, true);
foreach ($eachJson['search-results']['entry'] as $record) {
// array to store authors
$authors = [];
foreach ($record['author'] as $thisAuthor) { // **LINE 42**
// push initials and surname to array
array_push($authors, ($thisAuthor['initials'] . $thisAuthor['surname']));
};
// scopus ID
$scopusID = $record['dc:identifier'];
// paper title
$title = $record['dc:title'];
// date
$date = substr($record['prism:coverDate'], 0, 4);
// citations, if less than 4 then break out of iteration
if (!in_array(($cites = $record['citedby-count']), $ignore)) {
$cites = $record['citedby-count'];
} else {
break 2;
}
$thisData = [
"authors" => $authors,
"ID" => $scopusID,
"title" => $title,
"date" => $date,
"cites" => $cites
];
array_push($scopusData, $thisData);
}
};
// need to replace single quotes to avoid char escape
for ($i = 0; $i < count($scopusData); $i++) {
foreach ($scopusData[$i]['authors'] as &$edit) {
$edit = str_replace("'", "", $edit);
};
$scopusData[$i]['title'] = str_replace("'", "", $scopusData[$i]['title']);
};
I've highlighted line 42 which is causing the error. This must be something straightforward but it's been a long day and I can't figure out the problem! I still get the correct data at the end, the final array scopusData includes all the authors taken from that faulty foreach loop so it seems strange that I'm getting the error.

Answer 1

Are you sure that each record contains an author element?
Maybe you should add an ifset($record['author']) ahead of the foreach() loop.
(re-posted comment as an answer as OP's request)