php array_push with index and key

Adding like

$countryList["US"] = "United States";

Pushing a value into an array automatically creates a numeric key for it.

When adding a key-value pair to an array, you already have the key, you don't need one to be created for you. Pushing a key into an array doesn't make sense. You can only set the value of the specific key in the array.

// no key
array_push($array, $value);
// same as:
$array[] = $value;

// key already known
$array[$key] = $value

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