Preheat your oven to 400°F (200°C).
In a skillet over medium heat, add olive oil and minced garlic. Sauté for about 1 minute until fragrant.
Add the shredded chicken, oregano, basil, salt, and pepper to the skillet. Stir to combine and heat through for about 3-4 minutes.
Place the whole wheat pitas on a baking sheet. Spread ½ cup of marinara sauce evenly on each pita.
Top each pita with the garlic chicken mixture, followed by the chopped spinach and halved cherry tomatoes.
Sprinkle the shredded mozzarella cheese generously over the top of each pita.
Bake in the preheated oven for 10-12 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let cool for a minute. Garnish with fresh basil leaves if desired, then slice and serve.