How to loop over an array and conditionally update a nested value - php

Question

I have two arrays like:
array (size=4)
0 => string '5' (length=1)
1 => string '4' (length=1)
2 => string '2' (length=1)
3 => string '2' (length=1)
3 => string '8' (length=1)
and one array more that I load from an XML file:
object(SimpleXMLElement)[1]
public 'book' =>
array (size=101)
0 =>
object(SimpleXMLElement)[2]
public 'id' => string '1' (length=1)
public 'title' => string 'p' (length=1)
1 =>
object(SimpleXMLElement)[3]
public 'id' => string '2' (length=1)
public 'title' => string 'pp' (length=2)
2 =>
object(SimpleXMLElement)[4]
public 'id' => string '3' (length=1)
public 'title' => string 'pen' (length=3)
3 =>
object(SimpleXMLElement)[5]
public 'id' => string '4' (length=1)
public 'title' => string 'lapton' (length=6)
......
......
101 =>
object(SimpleXMLElement)[103]
public 'id' => string '101' (length=1)
public 'title' => string 'title' (length=5)
I want to compare each value of key id of second array with key of first array for each value. When it's the same, I want to update value of key title of second array.

Answer 1

Assuming your first array is $idArray and your second is $xmlArray, you could use something like this.
$result = array_map(function($xmlElement) use ($idArray) {
if (in_array($xmlElement->id, $idArray)) {
$xmlElement->title = 'updated value';
}
return $xmlElement;
}, $xmlArray);

Answer 2

Assumptions
the first array is called $array1
the second array is called $fromXML
the second array is not actually an array, it's a SimpleXMLElement with the following structure (psuedocode / JSONish syntax)
{
'book' => {
0 => SimpleXMLElement {
'id' => 1,
'title' => 'p'
}
}
}
I assume you can access the second array of elements with $fromXML['book']
I assume you can access an attribute of the first element with $fromXML['book'][0]['id']
I assume that you can set the text of the title of the first element with $fromXML['book'][0]['title'][0] = 'new title'
based on How can I set text value of SimpleXmlElement without using its parent? and PHP SimpleXML, how to set attributes? and PHP foreach change original array values
Solution
foreach($fromXML['book'] as $key => $element) {
if(array_key_exists($element['id'], $array1)) {
$fromXML['book'][$key]['title'][0] = $array1[$element->id];
}
}
Caveat and troubleshooting
I didn't test this, just going off of the documentation. If I've misinterpreted the structure of your SimpleXMLElement array, try experimenting with var_dump($fromXML['some']['key']) until you find the right way to access the array/element
Note: Apparently, array_key_exists() performs better than in_array() on large arrays

Answer 3

Try this for now
foreach($array1 as $arr1 => $val1){
foreach($array2 as $arr2 =>$val2){
if($arr1==$arr2){
$val2['title']='update value';
}
}
}