Question 42022 in PHP Question posted in
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Uncaught TypeError when only accessing certain keys within array – PHP

I am accessing an API using a cURL request in PHP. The response I receive contains the data I would expect, but when I loop through to process it, certain keys cause the error "Uncaught TypeError: Cannot access offset of type string on string." I’ve read through the numerous help questions here related to the error, but can’t find anything with how to address a situation where "some" array keys cause an error.

Edit #2: I have determined that for some reason, the order of declaring the variables below is causing the error. If I simply move declaring $transactionType above $transactionValue with no other changes, the code works. Why would the order of accessing those values cause the code to fail? All data from the array is returned as strings from the API. (Leaving original statements unedited to give context and meaning to other answers)

My code:

$curl = curl_init($urlAPI);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_HTTPHEADER, [
    'x-qn-api-version: 1',
    'Content-Type: application/json'
]);
$response = curl_exec($curl);
curl_close($curl);  
$decodedResponse = json_decode($response,true);
$transactionList = $decodedResponse["result"];
foreach($transactionList as $key => $value) {
  $timestamp = $value["timeStamp"];
  $hash = $value["hash"];
  $transactionValue = $value["value"];
  $transactionType = $value["functionName"];  //if I comment out this line with no other changes, it works as expected
  //Do stuff
}

As noted, if I comment out $transactionType it works perfectly and returns the 100+ results as expected. When I debug and print_r($transactionList), the functionName key exists in every result (sometimes is empty, though). Another item of interest is if I use isset to check the functionName key first, it cannot find any instances where it is set – even though print_r clearly shows it is. An example of the result from the API:

Array ( 
 [0] => Array ( 
  [timeStamp] => 1624666351 
  [hash] => 0x37f2ec62dbd3f812215ae2e82dcfb11feb56d27255ab10ee102d4ce29942a347
  [transactionIndex] => 95 
  [value] => 132506677002809378 
  [functionName] => )
 [1] => Array ( 
  [timeStamp] => 1624672333 
  [hash] => 0x9eebfa157829c632b58f743bbe7fb018add5de7a3881796cc6764e942cccf458
  [transactionIndex] => 133 
  [value] => 122506677002809378 
  [functionName] => swap(uint256 amountOutMin, address[] path, address to, uint256 deadline) )

Where am I going wrong with this where my code breaks if I try to access functionName?

Tags:

2

Answers


  1. 0 
    // This might helps.
<?php
foreach($transactionList as $key => $value) {
      $timestamp = $value["timeStamp"];
      $hash = $value["hash"];
      $transactionValue = $value["value"];
      //trying isset
       if(isset($value["functionName"])){
          //validate data
          $transactionType = $value["functionName"];
          //Do stuff
       }else{
       //debug the data
       }
      
    }
?>
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  2. 0

    UPDATE

    If you do not have complete control of all the code you may need to roll back from version 8.1. There is the same problem in a WordPress plugin so their only option was to roll back to 8.0.

    The entire error is "PHP Fatal error: Uncaught TypeError: Cannot
    access offset of type string on string in xxxx/index.php:47 Stack
    trace: #0 {main} thrown in xxxx/index.php on line 47" The error is in
    the error_log file generated post-error; the page displays nothing.
    Line 47 correlates to the $transactionType variable’s line. – 
    redstang423

    That is a completely different error than originally anticipated. The missing piece of the puzzle.

    My best guess is this is the problem in the swap() function returned by the API:

    [functionName] => swap(uint256 amountOutMin, address[] path, address to, uint256 deadline) )`

    I do not know what swap returns, but that may be the source of the type error.

    END OF UPDATE

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    It’s a type declaration issue.

    Type declarations can be added to function arguments, return values, and, as of PHP 7.4.0, class properties. They ensure that the value is of the specified type at call time, otherwise a TypeError is thrown.

    PHP Type declarations

    Your variable type must match the type declared in the function.
    You can change the type by using intval(), strval(), boolval(), etc.

    If you need pass $transactionType to a function or class as an integer, then you need to set the type:

    $transactionType = intval($value["functionName"]);

    Or if it needs to be a string value:

    $transactionType = strval($value["functionName"]);

    If necessary in your trouble shooting, you can use gettype() which returns the type.

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