  The isovalent-substituted iron-pnictide superconductor
SrFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ ($x$=0.35) has a slightly higher optimum
critical temperature than the similar system
BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$, and its parent compound SrFe$_{2}$As$_{2}$
has a much higher N\'eel temperature than BaFe$_{2}$As$_{2}$. We have studied
the band structure and the Fermi surfaces of optimally-doped
SrFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ by angle-resolved photoemission
spectroscopy (ARPES). Three holelike Fermi surfaces (FSs) around (0,0) and two
electronlike FSs around ($\pi$,$\pi$) have been observed as in the case of
BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$. Measurements with different photon
energies have revealed that one of the hole FSs is more strongly warped along
the $k_{z}$ direction than the corresponding one in
BaFe(As$_{1-x}$P$_{x}$)$_{2}$, while the electron FSs are almost cylindrical
unlike corrugated ones in BaFe(As$_{1-x}$P$_{x}$)$_{2}$. Comparison of the
ARPES data with first-principles band-structure calculation revealed that the
quasiparticle mass renormalization factors are different not only between bands
of different orbital character but also between the hole and electron FSs of
the same orbital character. By examining nesting conditions between the hole
and electron FSs, we conclude that magnetic interactions between FeAs layers
rather than FS nesting play an important role in stabilizing the
antiferromagnetic order. The insensitivity of superconductivity to the FS
nesting can be explained if only the $d_{xy}$ and/or $d_{xz/yz}$ orbitals are
active in inducing superconductivity or if FS nesting is not important for
superconductivity.
