run phpunit as another unit (suid)

eds.c

/*
*	This tool used to run PHPUnit tests by apache user
*/
    
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

#define KNRM  "\x1B[0m"
#define KRED  "\x1B[31m"
#define KGRN  "\x1B[32m"
#define KYEL  "\x1B[33m"
#define KBLU  "\x1B[34m"
#define KMAG  "\x1B[35m"
#define KCYN  "\x1B[36m"
#define KWHT  "\x1B[37m"

char* concat(char *s1, char *s2)
{
    char *result = malloc(strlen(s1)+strlen(s2)+1);//+1 for the zero-terminator
    strcpy(result, s1);
    strcat(result, s2);
    return result;
}

int main(int argc, char *argv[])
{
    char *command = "phpunit";
    int i, result = 0;
    printf("\n");
    printf("Effective UID\t= %d\n", geteuid());
    //printf("Real GID\t= %d\n", getgid());
    printf("Effective GID\t= %d\n\n", getegid());
    if( setgid(getegid()) ) perror( "set setgid" );
    if( setuid(geteuid()) ) perror( "set setuid" );
    
    for (i = 1; i < argc; i++) {
        printf("Param #%d is %s\n", i, argv[i]);
        command = concat(command, " ");
        command = concat(command, argv[i]);
    }

    printf("%sFinal command line: %s%s\n\n", KGRN, command, KNRM);
    return system(command);
}