  The Klein-Gordon equation for a scalar field sourced by a spherically
symmetric background is an interesting second-order differential equation with
applications in particle physics, astrophysics, and elsewhere. Here we present
solutions for generic source density profiles in the case where the scalar
field has no interactions or a mass term. For a $\lambda\phi^4$
self-interaction term, we provide the necessary expressions for a numerical
computation, an algorithm to numerically match the initial conditions from
infinity to the origin, and an accurate guess of that initial condition. We
also provide code to perform the numerical calculations that can be adapted for
arbitrary density profiles.

Computational Physics;High Energy Physics - Phenomenology;Classical Physics