/**
* Returns the value at an index of an array. This function simplifies the
* common pattern of checking for an index in an array and selecting a default
* value if it does not exist. You should NOT use `idx` as a general replacement
* for accessing array indices.
*
* `idx` is used to look for an index in an array, and return either the value
* at that index (if it exists) or some default (if it does not). Without
* `idx`, you need to do this:
*
* ```
* array_key_exists('index', $arr) ? $arr['index'] : $default
* ```
*
* This is verbose, and duplicates the variable name and index name, which can
* lead to errors. With `idx`, you can simplify the expression:
*
* ```
* idx($arr, 'index', $default);
* ```
*
* The value `$default` is optional, and defaults to null if unspecified.
*
* The array `$arr` is permitted to be null; if it is null, `idx` guarantees
* it will return `$default`.
*
* You should NOT use `idx` as a general replacement for accessing array
* indices. If you expect 'index' to always exist, DON'T use idx()!
*
* ```
* // COUNTEREXAMPLE
* idx($arr, 'index'); // If you expect 'index' to exist, this is WRONG!
* ```
*
* Instead, just access it normally like a sensible human being:
*
* ```
* $arr['index']
* ```
*
* This will give you a helpful warning if the index doesn't exist, allowing
* you to identify a bug in your program and fix it. In contrast, idx() will
* fail silently if the index doesn't exist, which won't help you out at all.
*
* `idx` is for default selection, not a blanket replacement for array access.
*
* Finally, you should NOT fix errors about array indexes in parts of the code
* you don't understand by just replacing an array access with a call to `idx`.
* This is sweeping the problem under the rug. Instead, you need to actually
* understand the problem and determine the most appropriate solution. It is
* possible that this really is `idx`, but you can only make that determination
* after understanding the context of the error.
*
* @param array $arr - Array to look for an index in.
* @param scalar $idx - Index to check for. No longer accepts negative integers
* for accessing elements from the end of the array.
* @param mixed $default - Default value to return if index is not found. By
* default, this is null.
* @return mixed Value at array index if it exists, or the default value if not.
*/
function idx($arr, $idx, $default = null)
{
if (\is_array($arr) || \is_vec($arr) || \is_dict($arr) || \is_keyset($arr)) {
return \hphp_array_idx($arr, $idx, $default);
}
if ($idx !== null) {
if (\is_object($arr)) {
if ($arr instanceof \ConstIndexAccess) {
if ($arr->containsKey($idx)) {
return $arr[$idx];
}
} else {
if ($arr instanceof \ConstSet) {
if ($arr->contains($idx)) {
return $idx;
}
} else {
if ($arr instanceof \ArrayAccess) {
if ($arr->offsetExists($idx)) {
return $arr->offsetGet($idx);
}
}
}
}
} else {
if (\is_string($arr)) {
if (isset($arr[$idx])) {
return $arr[(int) $idx];
}
}
}
}
return $default;
}
/**
* [__construct description]
* @param array $row
*/
public function __construct($row = array())
{
$this->import(is_dict($row) ? $row->export() : $row);
}
