Non-linear least squares fitting Issue

Modeling
2

I have tried to simply my model to fit a single gaussian and basing it off of this post. I am still unable to fit the model unfortunately

"""

functions {
    real phi(real x, real mu, real sigma){
        return 1 / (sigma * sqrt(2 * pi())) * exp(-(x - mu)^2/(2 * sigma^2));
    }
}

data {
 int<lower = 0> N;
 vector[N] y;
 vector[N] x;
}


parameters {
  real m;
  real<lower=0> sigma;
  real<lower=0> s;
}



model {
    //priors
    m ~ normal(0, 1);
    s ~ normal(0,1);
    sigma ~ normal(0,1);

    for(i in 1:N){
        y[i] ~ normal(phi(x[N], m, s),  sigma);
}
}
"""