You can’t just change a value that is serialized. I’ll explain why with part of your example
a:5: what follows is an array with 5 elements
{ start of first element
s:10: what follows is a string that is 10 characters long
"center_lat"; the index/key of the first element
s:16: what follows is a string that is 16 characters long
"50.3061818714249"; the value of the first element
You cannot change the text of a serialized array without adjusting each of the values in the string to adjust the length of that value.
There is no safe way to edit a serialized array. Any error and you will loose all content. The only way to safely edit the values is to unserialize, alter the values in the array and then re-serialize.
