Checking if array exists in another array

[NotionCommotion]

I didn't expect the following to work, but then tried it and it does.  Any gotchas I need to look out for?

<?php

$haystack=[
    (object)['a'=>1,'b'=>1,'c'=>1],
    (object)['a'=>1,'b'=>2,'c'=>1],
    (object)['a'=>2,'b'=>1,'c'=>2],
    (object)['a'=>2,'b'=>2,'c'=>1],
    (object)['a'=>2,'b'=>2,'c'=>2],
];

var_dump(in_array((object)['a'=>2,'b'=>2,'c'=>1],$haystack));  //True
var_dump(in_array((object)['a'=>1,'b'=>1,'c'=>2],$haystack));  //False

var_dump(in_array((object)['b'=>2,'a'=>2,'c'=>1],$haystack));  //True

Edited October 14, 2016 by NotionCommotion

[kicken]

Unless you perform a strict comparison (third parameter set to true) then PHP compares objects by checking each value.

 

Comparing Objects

When using the comparison operator (==), object variables are compared in a simple manner, namely: Two object instances are equal if they have the same attributes and values (values are compared with ==), and are instances of the same class.

In your cases all objects are instances of stdClass so they meet the same class requirement. After that it checks each key/value to see if they match. If you set the third parameter of in_array to true so it does a strict check then all three cases would be false because every value is it's own unique instance even if all the keys are the same.

 

Array's work similarly for a comparison so it would also work even if you had not cast them to objects first.

[NotionCommotion]

Thanks Kicken,

 

Yes, I had first tried this as arrays, and saw that it also worked.  What more surprised me was that ['a'=>1,'b'=>1,'c'=>2] and ['b'=>2,'a'=>2,'c'=>1] produced the same results.  I guess I expected that PHP would interpret them as their string equivalent.