Select index based on another array in PHP

Question

I have two arrays like this

Array
(
    [0] => 1
    [1] => 3
    [2] => 4
    [3] => 5
)

Array
(
    [0] => Array
        (
            [1] => Test1
            [2] => Location1
            [3] => Email1
            [4] => Name1
            [5] => Address1
            [6] => Age1
            [7] => Gender1
            [8] => Phone1
            [9] => Website1
            [10] => Cell1
        )

    [1] => Array
        (
            [1] => Test2
            [2] => Location2
            [3] => Email2
            [4] => Name2
            [5] => Address2
            [6] => Age2
            [7] => Gender2
            [8] => Phone2
            [9] => Website2
            [10] => Cell2
        )

    [2] => Array
        (
            [1] => Test3
            [2] => Location3
            [3] => Email3
            [4] => Name3
            [5] => Address3
            [6] => Age3
            [7] => Gender3
            [8] => Phone3
            [9] => Website3
            [10] => Cell3
        )
)

Now i have to select 1,3,4 and 5 index value from each second array. How can i do this without two loops. I know i will have to use one but i don't want to use two loops

Output Required

Array
(
    [0] => Array
        (
            [1] => Test1
            [3] => Email1
            [4] => Name1
            [5] => Address1

        )

    [1] => Array
        (
            [1] => Test2
            [3] => Email2
            [4] => Name2
            [5] => Address2
        )

    [2] => Array
        (
            [1] => Test3
            [3] => Email3
            [4] => Name3
            [5] => Address3
        )
)

using two loops is common. I want to know if there is any php built in function or logic so that i can achieve it — Muhammad Raheel
– Muhammad Raheel, Commented Feb 25, 2013 at 20:42
Using two loops isn't a bad thing. It won't make it any slower than one loop and some hackish code. On the upside, code readability will be better. — Mr. Llama
– Mr. Llama, Commented Feb 25, 2013 at 20:47
array_map in the rescue. A powerful tool which people often forget. — itachi
– itachi, Commented Feb 25, 2013 at 20:52

Michael Irigoyen · Accepted Answer · 2013-02-25 21:03:54Z

4

Using one loop, array_flip, and array_intersect_key, you can do it like this:

$array_one = array(1, 3, 4, 5);

$array_two = array(
    array(1 => 'Test1', 'Location1', 'Email1', 'Name1', 'Address1', 'Age1', 'Gender1', 'Phone1', 'Website1', 'Cell1'),
    array(1 => 'Test2', 'Location2', 'Email2', 'Name2', 'Address2', 'Age2', 'Gender2', 'Phone2', 'Website2', 'Cell2'),
    array(1 => 'Test3', 'Location3', 'Email3', 'Name3', 'Address3', 'Age3', 'Gender3', 'Phone3', 'Website3', 'Cell3')
); 

$array_one_flip = array_flip($array_one);
foreach($array_two as $k => $v) {
    $result[] = array_intersect_key($v, $array_one_flip);
}

print_r($result);

The result would be:

Array
(
    [0] => Array
        (
            [1] => Test1
            [3] => Email1
            [4] => Name1
            [5] => Address1
        )

    [1] => Array
        (
            [1] => Test2
            [3] => Email2
            [4] => Name2
            [5] => Address2
        )

    [2] => Array
        (
            [1] => Test3
            [3] => Email3
            [4] => Name3
            [5] => Address3
        )

)

edited Feb 25, 2013 at 21:03

answered Feb 25, 2013 at 20:55

Michael Irigoyen

23.1k18 gold badges92 silver badges132 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Jon Over a year ago

array_intersect_key uses the key value's and doesn't achieve OP's desired result.

Muhammad Raheel Over a year ago

Yes i have tested it is not working according to my requirement as you can see it is always selecting first 4 columns

Michael Irigoyen Over a year ago

Yeah, I overlooked that as well. I've modified my answer to address that issue.

jeroen · Accepted Answer · 2013-02-25 21:08:08Z

3

You could try it with array_intersect_key:

$keys = array_flip($keys_array);    // flip the keys array for matching with array_intersect_key
$result = array();
foreach ($content_array as $arr)
{
  $result[] = array_intersect_key($arr, $keys);
}

Working example on codepad. Thanks @Michael Irigoyen for the arrays...

edited Feb 25, 2013 at 21:08

answered Feb 25, 2013 at 20:55

jeroen

91.8k22 gold badges117 silver badges132 bronze badges

3 Comments

Muhammad Raheel Over a year ago

it is not selecting the desired result. Please test it

jeroen Over a year ago

@raheel shan Have you flipped your keys array?

jeroen Over a year ago

@raheel shan It does work, see my edit / the example on codepad.

Mike Brant · Accepted Answer · 2013-02-25 22:09:15Z

1

Just use an array_map function like this:

$keys_to_keep = array(1, 3, 4, 5);
$key_diff_array = array_fill_keys($keys_to_keep, 'not used');

$array; // your main array you want to filter assume value has been set elsewhere

$filtered_array = array_map(function ($value) use $key_diff_array {
    return array_intersect_key($value, $key_diff_array);
}, $array);

edited Feb 25, 2013 at 22:09

answered Feb 25, 2013 at 20:52

Mike Brant

71.4k10 gold badges102 silver badges104 bronze badges

1 Comment

user1646111 Over a year ago

I don't see $array in array_map?

user1646111 · Accepted Answer · 2013-02-25 21:07:06Z

0

using one loop:

<?php
 $selection = array(1, 3, 4, 5);
 for($i = 0; $i < count($array); $i++){

 reset($selection);
 $first = current($selection);
 $newarray[$i][$first] = $array[$i][$first];

 $next = next($selection);
 $newarray[$i][$next] = $array[$i][$next];

 $next = next($selection);
 $newarray[$i][$next] = $array[$i][$next];

 $next = next($selection);
 $newarray[$i][$next] = $array[$i][$next];
}
echo '<pre>';
print_r($newarray);

answered Feb 25, 2013 at 21:07

user1646111

1 Comment

Michael Irigoyen Over a year ago

Very inefficient way of doing it.

Community · Accepted Answer · 2020-06-20 09:12:55Z

You might also find this Note about array_flip useful.

Ensure that $array1 has values that can be accepted as array keys when flipped.

http://php.net/manual/en/language.types.array.php

The key can either be an integer or a string. The value can be of any type.

Additionally the following key casts will occur:

Strings containing valid integers will be cast to the integer type. E.g. the key "8" will actually be stored under 8. On the other hand "08" will not be cast, as it isn't a valid decimal integer. Floats are also cast to integers, which means that the fractional part will be truncated. E.g. the key 8.7 will actually be stored under 8. Bools are cast to integers, too, i.e. the key true will actually be stored under 1 and the key false under 0. Null will be cast to the empty string, i.e. the key null will actually be stored under "". Arrays and objects can not be used as keys. Doing so will result in a warning: Illegal offset type. If multiple elements in the array declaration use the same key, only the last one will be used as all others are overwritten.

http://www.php.net/manual/en/function.array-flip.php

array_flip() returns an array in flip order, i.e. keys from trans become values and values from trans become keys.

Note that the values of trans need to be valid keys, i.e. they need to be either integer or string. A warning will be emitted if a value has the wrong type, and the key/value pair in question will not be included in the result.

If a value has several occurrences, the latest key will be used as its value, and all others will be lost.

Collectives™ on Stack Overflow

Select index based on another array in PHP

5 Answers 5

3 Comments

3 Comments

1 Comment

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

3 Comments

3 Comments

1 Comment

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related