Return-1, what does that mean? Solution Solutions

Return-1, what does that mean?
function MyFunction ($v 1, $v 2) {if ($v 1=== $v 2) {return 0;
} if ($v 1> $v 2) {return 1;
} else {return-1;
}} $a 1=array (0=> "Dog",1=> "Cat",2=> "Horse");
$a 2=array (3=> "Dog",1=> "Cat",5=> "Horse");
Print_r (ARRAY_DIFF_UASSOC ($a 1, $a 2, "myfunction"));
?>
The result of the operation is this: Array ([0] = Dog [2] = = Horse)
So the return of 0, 1,-1. I just do not understand here, has been 0, 1 of the understanding is true and false, then-1?
What's the effect of return-1? More details, please.

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The custom return value. In that function,-1 is the other condition.
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Incoming parameters $v 1, $v 2
1 means $v 1 is greater than $v 2
-1 means $v 1 is less than $v 2
0 means $v 1 equals $v 2

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Incoming parameters $v 1, $v 2
1 means $v 1 is greater than $v 2
-1 means $v 1 is less than $v 2
0 means $v 1 equals $v 2

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Custom functions, comparing index values ... That's usually the way it's written.

The 1,0,-1 here indicate greater than, equal to, less than

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