Select index based on another array in PHP - 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
)
)

Answer 1

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
)
)

Answer 2

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...

Answer 3

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);

Answer 4

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);

Answer 5

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.