When encountering PHP errors like "Illegal string offset," what resources or knowledge should a developer have to troubleshoot and fix the issue effectively?

When encountering a PHP error like "Illegal string offset," it typically means that you are trying to access an array using a string key that does not exist. To fix this issue, you should ensure that you are accessing array elements using numerical indexes or valid keys. You can also use functions like `isset()` or `array_key_exists()` to check if a key exists before accessing it.

// Example code snippet to fix "Illegal string offset" error
$array = array('key1' => 'value1', 'key2' => 'value2');

// Check if key exists before accessing it
if (isset($array['key1'])) {
    echo $array['key1'];
} else {
    echo 'Key does not exist';
}