PHP mapping one array to another but with different key locations

Question

I would like to map values in two arrays which have different shapes, as follows:

$array1=array(
    1=>array(1=>'apple', 2=>'banana', 3=>'cherry'),
    2=>array(1=>'david', 2=>'eddie', 3=>'frank'),
);

Now:

$array2=array(
    1=>'apple',
    2=>'banana',
    3=>'cherry',
    4=>'david',
    5=>'eddie',
    6=>'frank',
);

Such that when the value of $array1[2][3] is changed from frank to paula for example, then the value of $array2[6] is changed similarly.

How would I do this? NOTE: the keys will not change in quantity once declared.

If you want to keep the two array structures in sync, then you'll have to rebuild $array2 whenever $array1 changes. One could use references, but that would require manual array building. A virtual ArrayObject that automaps it might be another option. — mario
– mario, Commented Apr 7, 2015 at 9:00

mrun · Accepted Answer · 2015-04-07 11:30:50Z

Do you have the freedom to build the $array2 in another way? If you do, then this is how you can go about the 'linked' arrays:

<?php

$array1=array(
    1=>array(1=>'apple', 2=>'banana', 3=>'cherry'),
    2=>array(1=>'david', 2=>'eddie', 3=>'frank'),
);
$array2=array(
    1=>'apple',
    2=>'banana',
    3=>'cherry',
    4=>'david',
    5=>'eddie',
    // Assign by reference $array1[2][3] (currently holding 'frank')
    6=>&$array1[2][3],
);
// This will print the initial state of $array2
echo '<pre>';print_r( $array2 );echo '</pre>';
// Now change the value in $array1
$array1[2][3] = 'paula';
// And since $array2 'points' to the same memory location it will get
// changed too (well technically it won't but that's not important)
echo '<pre>';print_r( $array2 );echo '</pre>';

For more information about assignment by reference you can check this out

dev1234 · Accepted Answer · 2015-04-07 08:58:06Z

1

Please use array merge, here is how it will help you.

<?php
$a1=array("red","green");
$a2=array("blue","yellow");
print_r(array_merge($a1,$a2));
?>

will output,

Array ( [0] => red [1] => green [2] => blue [3] => yellow )

to learn more, http://php.net/manual/en/function.array-merge.php

answered Apr 7, 2015 at 8:58

dev1234

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Comments

aΨVaN · Accepted Answer · 2015-04-07 10:16:28Z

1

<?php


$array1=array(
    1=>array(1=>'apple', 2=>'banana', 3=>'cherry'),
    2=>array(1=>'david', 2=>'eddie', 3=>'frank'),
);
$op = array();

foreach($array1 as $key =>$index){
    $op =array_merge($array1[1],$array1[2]);
}

print_r(  $op);
?>

Use array_merge to merge two arrays

answered Apr 7, 2015 at 10:16

aΨVaN

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1 Comment

Oliver Williams Over a year ago

that is not very useful. It is hard coded to 1 and 2, and merging wouldn't create an array which changes as the first one did. @mrun post is correct.

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