Change just 1 key in a serialised array with 3 keys using php function

I am trying to import values which are stored as a serialised array with 3 keys like this:

a:3:{i:754;s:0:"";i:753;s:0:"";i:752;s:0:"";}

Would anyone know a php function to change the value within 1 key (adjust 754) and leave the other keys as they were?

I’m using WP ALL Import and i can match my records and adjust the value for 754, but it changes the entire serialised array, deleting the other values in the other 2 keys

Thank you in advance

>Solution :

This would replace the value of array Occurance 754

$serial = 'a:3:{i:754;s:0:"";i:753;s:0:"";i:752;s:0:"";}';

$arr = unserialize($serial);

$arr[754] = 'NEW';
print_r($arr);
echo $serial = serialize($arr);

RESULT

Array
(
    [754] => NEW
    [753] => 
    [752] => 
)
a:3:{i:754;s:3:"NEW";i:753;s:0:"";i:752;s:0:"";}