Can I use an instantiated Object as an Array Key?

Question

For example:

$product = new Product("cat");  if(isset($sales[$product])){      $sales[$product]++; } else{      $sales[$product] = 1; } 

Answer 1

From the docs:

Arrays and objects can not be used as keys. Doing so will result in a warning: Illegal offset type.

You could give each instance a unique ID or override __toString() such that it returns something unique and do e.g.

$array[(string) $instance] = 42; 

Answer 2

You can use http://www.php.net/manual/en/class.splobjectstorage.php

$product = new Product("cat"); $sales = new SplObjectStorage(); if(isset($sales[$product])){      $sales[$product]++; } else{      $sales[$product] = 1; } 

It's not a real array, but has a decent amount of array-like functionality and syntax. However, due to it being an object, it behaves like a misfit in php due to its odd foreach behavior, and its incompatibility with all the native php array functions. Sometimes you'll find it useful to convert it to a real array via

$arr = iterator_to_array($sales); 

so it plays nice with the rest of your codebase.