What does the error "Undefined array key 1" in PHP typically indicate?

The error "Undefined array key 1" in PHP typically indicates that you are trying to access an array element using a key that does not exist in the array. This error can occur when trying to access an element in an array using a specific key that has not been defined. To solve this issue, you should first check if the key exists in the array before trying to access it to avoid the error.

if (array_key_exists(1, $array)) {
    // Access the element with key 1
    $value = $array[1];
} else {
    // Handle the case when the key does not exist in the array
    echo "Key 1 does not exist in the array";
}