Checking equality of variables in array

Question

I want a PHP program to tell if an array contains any equal data. For that I'm writing this code but it always returns false, even though I have given equal values at position array position 1 and 2. Can anyone help me find out what is wrong with this code?

$a[0]=qwe;
$a[1]=abc;
$a[2]=abc;
$a[3]=xyz;

if(is_equal($a))
{
   echo "True";
}
else
{
   echo "False";
}

function is_equal($a)
{
    $size=sizeof($a);
    for ($i = 0; $i <= $size-2; $i++)
    {
        if ($a[i] === $a[i+1])
        {
            return true;
        }
    }
    return false;   
}

The number of items in the array is count($a), not sizeof($a), I think. Are you not missing some quotes in the first four lines? — CompuChip
– CompuChip, Commented Nov 26, 2013 at 14:51
@CompuChip Have you read the manual? sizeof is an alias of count ;) — kero
– kero, Commented Nov 26, 2013 at 14:52

Community · Accepted Answer · 2023-11-17 20:42:18Z

5

You don't need to write a function for that, you can use array_unique:

if ($array !== array_unique($array))
{
  // There were duplicate values
}

edited Nov 17, 2023 at 20:42

CommunityBot

11 silver badge

answered Nov 26, 2013 at 14:50

jeroen

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4 Comments

Laurent S. Over a year ago

True but what if the goal is to identify unique or non-unique values ? Or, as the code might indicate, to identify consecutive identical values, ignoring them if they're not consecutive... From where I see it array_unique() is to PHP what distinct is to SQL

jeroen Over a year ago

@Bartdude There are other built-in array functions to get for example the difference if the OP should need that. From how I read the question, this is all the OP needs, but it could always be adapted according to the exact specifications.

user3036851 Over a year ago

can u plz elaborate it, actually i m new to php

jeroen Over a year ago

@user3036851 There is not much more to it, if you want you can replace the contents of your whole function with return ($a !== array_unique($a)); and that is about it.

Mark Baker · Accepted Answer · 2013-11-26 14:55:44Z

2

The problem with your existing code is that

if ($a[i] === $a[i+1])

should be

if ($a[$i] === $a[$i+1])

PHP variables start with a $, otherwise i is treated as a constant, and as the constant isn't defined, then a string value of "i"

$a["i"] doesn't exist, therefore it can never be equal to anything; and $a[i+1] will add 1 to i giving 1, so it is always a comparison of a non-existent array element against element 1

answered Nov 26, 2013 at 14:55

Mark Baker

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