array_intersect throws errors when arrays have sub-arrays

Question

I'm trying to use array_intersect to compare two arrays of arrays.

$start[]=array(
        'id'=>1,
        'name'=>'Up',
        'action'=>'up'
);
$start[]=array(
        'id'=>3,
        'name'=>'Down',
        'action'=>'down'
);
$start[]=array(
        'id'=>5,
        'name'=>'Left',
        'action'=>'left'
);




$end[]=array(
        'id'=>1,
        'name'=>'Up',
        'action'=>'up'
);
$end[]=array(
        'id'=>9,
        'name'=>'Up',
        'action'=>'up'
);

$result=array_intersect($start,$end);

However, I always get the notice message:

Notice: Array to string conversion in testfile.php on line xyz

And the comparison doesn't actually occur.

What is the best way to compare the two arrays without reinventing the wheel or arriving at something overly complex?

SamA · Accepted Answer · 2013-09-25 16:26:48Z

6

The array_diff and array_intersect convert each element in the primary array in to a string for comparison. If you would like a different comparison, then you could use the callback method with the following built-in functions:

array_uintersect_assoc() - Computes the intersection of arrays with additional index check, compares data by a callback function
array_intersect_uassoc() - Computes the intersection of arrays with additional index check, compares indexes by a callback function
array_uintersect_uassoc() - Computes the intersection of arrays with additional index check, compares data and indexes by a callback functions

I found these by searching PHP.net for the function array_diff and followed the related function links. Its a great way to see alternatives for doing something.

answered Sep 25, 2013 at 16:26

SamA

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10 Comments

Force Flow Over a year ago

There is no additional index to check against. None of those functions solve the issue by themselves. What would I call back?

SamA Over a year ago

Well, if its ALWAYS a two-dimensional array a callback to another array compare function would work. Another, purpose-built function could be written as well. The idea is to let PHP do the iterating and just to write the compare function as dictated by the given situation.

Force Flow Over a year ago

I don't have an additional index to supply--and I'm not even sure that the index check is supposed to do. What comparison callback function would be appropriate?

SamA Over a year ago

The index checking is just another level of array compare. If its not needed, a callback that always returns "index match" would work. Here is another answer on Stack Overflow that might be of some use: stackoverflow.com/questions/3876435/recursive-array-diff

Force Flow Over a year ago

That's diff, not intersect.

|

Force Flow · Accepted Answer · 2013-09-25 19:15:30Z

2

Someone else elsewhere suggested array_map and serialize. I ended up coming up with this--which is certainly much easier than nesting and recursion and failing miserably in an attempt to basically rewrite the array_intersect function.

echo '<pre>';

$start[]=array(
        'id'=>1,
        'name'=>'Up',
        'action'=>'up'
);
$start[]=array(
        'id'=>3,
        'name'=>'Down',
        'action'=>'down'
);
$start[]=array(
        'id'=>5,
        'name'=>'Left',
        'action'=>'left'
);
$start[]=array(
        'id'=>2,
        'name'=>'Left',
        'action'=>'left'
);





$end[]=array(
        'name'=>'Up',
        'id'=>1,

        'action'=>'up'
);
$end[]=array(
        'id'=>8,
        'name'=>'Right',
        'action'=>'Right'
);




function serialize_array_values($arr){
    foreach($arr as $key=>$val){
        sort($val);
        $arr[$key]=serialize($val);
    }

    return $arr;
}




$result = array_map("unserialize", array_intersect(serialize_array_values($start),serialize_array_values($end)));

echo "\n\n\n";
echo var_dump($result);


echo '</pre>';

answered Sep 25, 2013 at 19:15

Force Flow

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1 Comment

Vikas Chauhan Over a year ago

this breaks my original array

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