how to sum up values of single dimentional array having same key in php : <p>For example: if strArr is ["B:-1", "A:1", "B:3", "A:5"] then your program should return the string A:6,B:2.</p>

<p>Your final output string should return the keys in alphabetical order. Exclude keys that have a value of 0 after being summed up.
Examples
Input: array("X:-1", "Y:1", "X:-4", "B:3", "X:5")
Output: B:3,Y:1</p>
