Results of https://gist.github.com/msonnabaum/5052884

no xhprof_enable()

---
extension:
  min: "0.0229"
  max: "0.3490"
  mean: "0.0805"
  median: "0.0575"
  95th: "0.1972"
...
---
symfony:
  min: "0.0451"
  max: "10.1361"
  mean: "1.4396"
  median: "0.7205"
  95th: "5.2242"
...

xhprof enabled no CPU flag

---
extension:
  min: "0.0241"
  max: "0.3629"
  mean: "0.0824"
  median: "0.0595"
  95th: "0.2085"
...
---
symfony:
  min: "0.0789"
  max: "25.6009"
  mean: "3.4071"
  median: "1.5434"
  95th: "12.0888"
...

xhprof enabled with CPU flag

---
extension:
  min: "0.0248"
  max: "0.3541"
  mean: "0.0872"
  median: "0.0596"
  95th: "0.2215"
...
---
symfony:
  min: "0.1099"
  max: "38.0888"
  mean: "5.2778"
  median: "2.2751"
  95th: "19.2007"
...