What does the error message "Warning: array_merge(): Argument #2 is not an array" indicate in PHP code?

The error message "Warning: array_merge(): Argument #2 is not an array" indicates that the function array_merge() is expecting the second argument to be an array, but it is not. To solve this issue, you need to ensure that the second argument passed to array_merge() is indeed an array. This can be done by checking the variable type before passing it to array_merge().

// Check if the second argument is an array before merging
if (is_array($secondArray)) {
    $mergedArray = array_merge($firstArray, $secondArray);
} else {
    // Handle the case where the second argument is not an array
    echo "Error: Second argument is not an array";
}