ambiguates old declaration

[Binbasi]

#include <stdio.h>
#include <string.h>
 
void strrev (char *string)
{
        int len=strlen(string);
        char string2[20];
        for(int i=0; i<len; i++){
                string2[i]=string[len-1-i];
                }
 
     }
 
int main(){
    char string[20]="Program";
    strrev(string);
 
    return 0;
    }
 
 

I am trying to write a simple code to reverse a character string. But at line 5 i am getting the following error:
new declaration `void strrev(char*)'


What is my mistake. And how can I port the reversed word from void into main?

Thank you for your answers

[weaknessforcats]

You have inadvertently used the name strrev for your function and this is also the same name as the C library function strrev.

In C function names must be unique.

You have to change the name of your function.