Let's see a lyric of "In the city of love"- Phineas and Ferb.
We could share a crêpe sucrée at this Parisian café
Isn't this a perfect day? How do I look in this beret?
Oh Phineas... Won't you share a crème brûlée with me?
How perfect could this be 
In the city of love?
In the City of Love 
In the City of Love 
In the City of Love 
We could try some fancy cheese
Or peruse the galleries
“I wonder if oil-based paint  is combustible...as a rocket fuel.”
 Isn't this a perfect day?
 How do I look in this beret?
 “That reminds me! 
 We might need helmets.”
 Oh, how can he not feel the same way
 When we're strolling down  the Champs-Élysées
 In the City of Love
 In the City of Love
 In the City... 
I wish that he would whisper "ma chérie, je t'aime" 
But all he wants to do is
try to fix that plane
 In the City of Love
 In the City of Love
 In the City of Love
 In the City of Love
 In the City of Love...
The lyric is the word of Isabella. She loves Phineas but he isn't realized this love.
"In the city of love" have a light melody that makes audiences feeling the love of Isabella. With the Parisian view, we can be feeling simple love. Some light, some food, some activities. That makes love favor.
The things I like about this song is the lyric, meaning, and especially the picture behind the activity. 
In this song, Phineas and Isabella walking on the Parisian street, Champs-Élysées. Isabella wants him to know she loves him. Phineas just things about his plan. When the painter gives Isabella her picture. We see that Phineas concentrates on the building of the streets. Isabella wants his attention to her. When both walk into the park, we see everybody has a couple but Phineas uninteresting, Isabella walks behind, she has a little sad.
Let's watch this video and follow the melody