Each of you should look not only to your own interests, but also to the interests of others. Your attitude should be the same as that of Christ Jesus: Who, being in very nature God, did not consider equality with God something to be grasped,
but made himself nothing,
taking the very nature of a servant,
being made in human likeness.
And being found in appearance as a man,
he humbled himself
and became obedient to death—
even death on a cross!
Therefore God exalted him to the highest place
and gave him the name that is above every name,
that at the name of Jesus every knee should bow,
in heaven and on earth and under the earth,
and every tongue confess that Jesus Christ is Lord,
to the glory of God the Father. [Philippians 2:4-11]
a girl who speaks
a girl who speaks 
I want to know what sort of spiritual experience happened to Paul in jail that inspired him to write a letter like Philippians – which could have just been a brief thank you note, but turned out to be one of the most (if not the most) ecstatic expressions of joy and praise he, or any apostle ever wrote.
I think Jesus was in the jail cell with him.
Do you mean physically in the jail cell with him?