/**
* 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:
*
* $arr['index']
*
* This will give you a helpful warning if the index doesn't exist, allowing
* you to identify a bug in your program and fix it. In contrast, idx() will
* fail silently if the index doesn't exist, which won't help you out at all.
*
* idx() is for default selection, not a blanket replacement for array access.
*
* Finally, you should NOT fix errors about array indexes in parts of the code
* you don't understand by just replacing an array access with a call to idx().
* This is sweeping the problem under the rug. Instead, you need to actually
* understand the problem and determine the most appropriate solution. It is
* possible that this really is idx(), but you can only make that determination
* after understanding the context of the error.
*
* @param array Array to look for an index in.
* @param scalar Index to check for. No longer accepts negative integers for
* accessing elements from the end of the array.
* @param mixed Default value to return if index is not found. By default,
* this is null.
* @return mixed Value at array index if it exists, or the default value
* if not.
*/
function idx($arr, $idx, $default = null)
{
if (\is_array($arr)) {
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 $arr[$idx];
}
}
}
}
return $default;
}
function main()
{
$a = array('1' => '2', 'hello' => 'world', '' => 'empty');
$b = null;
var_dump(hphp_array_idx($a, '1', 3));
var_dump(hphp_array_idx($a, '0', 4));
var_dump(hphp_array_idx($a, 1, 5));
var_dump(hphp_array_idx($a, 0, 6));
var_dump(hphp_array_idx($a, 1.01, 7));
var_dump(hphp_array_idx($a, true, 8));
var_dump(hphp_array_idx($a, false, 9));
var_dump(hphp_array_idx($a, 'hello', 10));
var_dump(hphp_array_idx($a, 'world', 11));
var_dump(hphp_array_idx($a, '', 12));
var_dump(hphp_array_idx($a, null, 13));
// should fatal
var_dump(hphp_array_idx($b, 'not_reached', 14));
}