Message: Trying to Access Array Offset on Value of Type Null

Message: Trying to access array offset on value of type null

This happens because $cOTLdata is not null but the index 'char_data' does not exist. Previous versions of PHP may have been less strict on such mistakes and silently swallowed the error / notice while 7.4 does not do this anymore.

To check whether the index exists or not you can use isset():

isset($cOTLdata['char_data'])

Which means the line should look something like this:

$len = isset($cOTLdata['char_data']) ? count($cOTLdata['char_data']) : 0;

Note I switched the then and else cases of the ternary operator since === null is essentially what isset already does (but in the positive case).

How to fix Trying to access array offset on value of type null error

When you receive this error after fetching data from the database then it means that the database didn't found any matching rows. Most database fetching functions return either null or an empty array when there are no matching records or when the result set has been exhausted.

To solve the problem you need to check for the truthiness of the value or for the existence of the key that you want to access.

$monday_lectures = "SELECT * from lectures where lecture_time = '11am to 1pm' and lecture_day = 'firday'";
$result_11to1 = mysqli_query($con, $monday_lectures);
$m11to1 = mysqli_fetch_array($result_11to1);
if ($m11to1 && $m11to1["lecture_day"] == !'') {
    echo "<td>".$m11to1["lecture_name"]."</td>";
} else {
    echo "<td> no class</td>";
}

If what you are after is a single value from the result array then you can specify a default in case the result is not present.

$monday_lectures = "SELECT * from lectures where lecture_time = '11am to 1pm' and lecture_day = 'firday'";
$result_11to1 = mysqli_query($con, $monday_lectures);
$m11to1 = mysqli_fetch_array($result_11to1);
$lecture = $m11to1["lecture_day"] ?? null;

The same applies to PDO.

$monday_lectures = $pdo->prepare("SELECT * from lectures where lecture_time = '11am to 1pm' and lecture_day = 'firday'");
$monday_lectures->execute();
$m11to1 = $monday_lectures->fetch();
$lecture = $m11to1["lecture_day"] ?? null;

Trying to access array offset on value of type null for array populated from MySQLi result set

mysqli_fetch_row will return null at some point (as it always does when it runs out of rows to retrieve, as per the documentation). But you're not checking that before trying to read its 0th index, hence the error.

Many people retrieve rows using this kind of style:

while ($row = mysqli_fetch_row($result)) { 
  $resultArray[] = $row[0]; 
}

which will avoid this sort of problem. That's the way you'll often see it done in examples and documentation, too.

Error: Trying to access array offset on value of type null in my PHP code

Problem

This line:

$screens = json_decode( str_replace( '`', '"', $code ), true );

will make the json invalid before you're trying to decode it.

Imagine you have a string like this:

$json = '{"foo": "lorem `bar` ipsum"}';

If you run your current str_replace() on it before trying to decode the string, it will become:

$json = '{"foo": "lorem "bar" ipsum"}';

See the issues with the quotes? If you try to decode that using json_decode(), it will fail and return null, which means that $screens['kc-css'] will throw the error message you're getting.

Solution

You need to escape the double quote with a backslash: \" if you want to use a literal double quote inside a double quoted string.

Change it to:

$screens = json_decode( str_replace( '`', '\"', $code ), true );

and it should work.

Here's a demo

How to solve Trying to access array offset on value of type null in Codeigniter 4

Since you don't have a " firstOrFail " function, you should add a try catch around your code at

$dataMember = $M_admin->where("unm",
            $member_username)->first(); 

You probably don't want to do the full check process if an user doesn't exist, you can also add a simple " if(!empty($dataMember))" but adding too much logic in your controller is probably not the best way, at least you should create a private function who do the full checking logic and return " true " or " err = "your_error_message"

I hope my answer can help you. :)

---

Related Topics