Returns the value at an index of an array
namespace HH; function idx<Tk, Tv>( ?KeyedContainer<Tk,Tv> $collection, $index, mixed $default = NULL, );
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);
$default is optional, and defaults to null if unspecified.
$arr is permitted to be null; if it is null,
it will return
You should NOT use
idx as a general replacement for accessing array
indices. If you expect 'index' to always exist, DON'T use idx()!
// COUNTEREXAMPLE idx($arr, 'index'); // If you expect 'index' to exist, this is WRONG!
Instead, just access it normally like a sensible human being:
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
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.
mixed $default = NULL- Default value to return if index is not found. By default, this is null.
mixed- Value at array index if it exists, or the default value if not.