C Passing Pointer to Array to Function Issue

Googled around and can't find out what's going wrong here, the pointer gets passed correctly but it's not working.

The program is supposed to find the length of the character array/string.

What's wrong here? Just always give length of zero!

#include <stdio.h>
#include <stdbool.h>

int stringlength(char *); // Declare function in the beggining (because C)

main()
{
    char testString[100]; // Character array where we'll store input from command line (unsafely)
    char *arrayPointer; // Pointer that will point to array so it can be passed to function
    int length; // Integer for length of string
    printf("Please enter in a string: \n");
    scanf("s", &testString[0]); // Get input
    arrayPointer = &testString[0]; // Point the pointer to the array
    printf("Pointer to array %p\n-----------------\n", arrayPointer); // Output pointer
    stringlength(arrayPointer); // And use the function
    printf("Length is %d\n", length); // Output the length of the string...
}

stringlength(char *stringArray)
{
    int i = 0; // Counter variable
    int length = 0; // Length variable
    bool done = false; // Boolean for loop
    while(!done)
    {
        printf("Character is %c\n", stringArray[i]); // Output character
        printf("Memory location %p\n", &stringArray[i]); // Output memory location of character

        if(stringArray[i] == '\x00') // If the current array slot is a null byte we've reached the end of the array
        {
            done = true; // Null byte found, we're all done here
            return length;
        } else {
            length++; // Not a null byte so increment length!
        }
        i++; // Counter for moving forward in array
    }
}

Output of this is:

mandatory@MANDATORY:~/Programming/C$ ./a.out
Please enter in a string: 
testing
Pointer to array 0x7fffc83b75b0
-----------------
Character is    
Memory location 0x7fffc83b75b0
Character is 
Memory location 0x7fffc83b75b1
Length is 0