Multidimenssion array compare two arrays and update first array value - php

Question

I want to filter a array by a number and update its status in the first array.
I have two array $arr1,$arr2
$arr1 = array(
0=>array('number'=>100,name=>'john'),
1=>array('number'=>200,name=>'johnny')
);
$arr2= array(
0=>array('number'=>300,name=>'r'),
1=>array('number'=>100,name=>'b'),
2=>array('number'=>200,name=>'c')
);
Final output should be an array like this
$arr1 = array(
0=>array('number'=>100,name=>'b'),
1=>array('number'=>200,name=>'c')
);
Any ideas to start off please ?

Answer 1

For specialized array modifications like this, the method of choice is array walk. It allows you to apply a custom function to each element in a given array.
Now, because of your data format, you will have to do a loop. Wrikken is asking if you can retrieve or transform the data to provide faster access. The algorithm below is O(n^2): it will require as many cycles as there are elements in the first array times the number of elements in the second array, or exactly count($arr1) * count($arr2).
function updateNameFromArray($element, $key, $arr2) {
foreach($arr2 as $value) {
if($value['number'] == $element['number']) {
$element['name'] == $value['name'];
break;
}
}
}
array_walk($arr1, "updateNameFromArray", $arr2);
Now, what Wrikken is suggesting is that if your arrays can be changed to be keyed on the 'number' property instead, then the search/replace operation is much easier. So if this were your data instead:
$arr1 = array(
100=>array('number'=>100,name=>'john'),
200=>array('number'=>200,name=>'johnny')
);
// notice the keys are 100 and 200 instead of 0,1
$arr2= array(
300=>array('number'=>300,name=>'r'),
100=>array('number'=>100,name=>'b'),
200=>array('number'=>200,name=>'c')
);
// notice the keys are 300, 100 and 200 instead of 0,1, 2
Then you could do this in O(n) time, with only looping over the first array.
foreach($arr1 as $key => $value) {
if(isset($arr2[$key])) {
$value['number'] = $arr2[$key]['number'];
}
}

Answer 2

Try this. It's not that clean but i think it would work.
<?php
$arr1 = array(0=>array('number'=>100,'name'=>'john'),1=>array('number'=>200,'name'=>'johnny'));
$arr2= array(0=>array('number'=>300,'name'=>'r'),1=>array('number'=>100,'name'=>'b'),2=>array('number'=>200,'name'=>'c'));
foreach( $arr1 as $key=>$data1 )
{
foreach( $arr2 as $key2=>$data2 )
{
if( $data1['number'] == $data2['number'] )
{
$arr1[$key]['name'] = $arr2[$key2]['name'];
}
}
}
print_r( $arr1 );
?>
the output would be :
Array
(
[0] => Array
(
[number] => 100
[name] => b
)
[1] => Array
(
[number] => 200
[name] => c
)
)

Answer 3

There isn't really a simple way for this to be accomplished with generic PHP functions, so, You might need to create mapping arrays.
The way I would approach this, is creating a loop that goes through the first array, and maps the number value as a key to the index of it's place in $arr1 giving you:
$tmp1 = array();
foreach ($arr1 as $key => $number_name) {
$tmp1[$number_name['number']] = $key;
}
This should give you an array that looks like
$tmp1 [
100 => 0,
200 => 1
];
Then I would loop through the second array, get the number value, if that existed as a key in $tmp1, get the associated value (being the key for $arr1), and use that to update the name in $arr1.
// Loop through $arr2
foreach ($arr2 as $number_name) {
// Get the number value
$number = $number_name['number'];
// Find the $arr1 index
if (isset($tmp1[$number])) {
$arr1_key = $tmp1[$number];
// Set the $arr1 name value
$arr1[$arr1_key]['name'] = $number_name['name'];
}
}

Answer 4

<?php
//Set the arrays
$arr1 = array(
array('number'=>100,'name'=>'john'),
array('number'=>200,'name'=>'johnny')
);
$arr2= array(
array('number'=>300,'name'=>'r'),
array('number'=>100,'name'=>'b'),
array('number'=>200,'name'=>'c')
);
// use a nested for loop to iterate and compare both arrays
for ($i=0;$i<count($arr1);$i++):
for ($j=0;$j<count($arr2);$j++):
if ($arr2[$j]['number']==$arr1[$i]['number'])
$arr1[$i]['name']=$arr2[$j]['name'];
endfor;
endfor;
print_r($arr1);
OUTPUT:
Array (
[0] => Array ( [number] => 100 [name] => b )
[1] => Array ( [number] => 200 [name] => c )
)
That being said, you should probably reconsider the very way your data is structured. Do you really need a multi-dimensional array or can you use a simple associative array, like so:
// set the arrays
$arr1 = array(
'john'=>100,
'johnny'=>200
);
$arr2 = array(
'r'=>300,
'b'=>100,
'c'=>200
);
// find values in arr2 common to both arrays
$arr3 = array_intersect($arr2, $arr1);
// change the key of arr1 to match the corresponding key in arr2
foreach ($arr3 as $key=>$value) {
$old_key = array_search($value, $arr1);
$arr1[$key]=$arr1[$old_key];
unset($arr1[$old_key]);
}
print_r($arr1);
OUTPUT:
Array (
[b] => 100
[c] => 200
)