to estimate the endpoint contributions, and expressed as $$\int_0^1 \frac{dx}{x} \to
 X_A = (1+ \rho_A e^{i\phi_A})
 \ln \frac{m_B}{\Lambda_h}
 \label{XA},$$ where $\Lambda_h$ $=$ $0.5$ GeV. For spectator scattering contributions, the calculation of twist-3 distribution amplitudes also suffers from endpoint divergence, which is usually dealt with the same manner as Eq.(\[XA\]) and labelled by $X_H$ [@Beneke2]. Moreover, a quantity $\lambda_B$ is used to parameterize our ignorance about $B$-meson distribution amplitude \[see Eq.(\[hardblock\])\] through [@Beneke2] $$\int_0^1 \frac{ d \xi }{\xi} \Phi_B(\xi)
 \ \equiv \ \frac{m_B}{\lambda_B}
 \label{lamdef}.$$

The QCDF approach itself cannot give information or/and constraint on the phenomenological parameters of $X_A$, $X_H$ and ${\lambda_B}$. These parameters should be determined from experimental data. To conform with measurements of nonleptonic $B$ ${\to}$ $PP$ decays, we will adopt a similar method used in Ref.[@zhu2] to deal with the contributions from weak annihilation and spectator scattering. Focusing on the flavor dependence, without consideration of theoretical uncertainties, annihilation contributions are reevaluated in detail [@zhu2] to explain the ${\pi}K$ puzzle and the recent measurements on pure annihilation decays $\bar{B}_{s}^{0}$ ${\to}$ ${\pi}^{+}{\pi}^{-}$ and $\bar{B}_{d}^{0}$ ${\to}$ $K^{+}K^{-}$ \[see Eq.(\[HFAGpipi\],\[HFAGKK\])\]. The authors of Ref. [@zhu2] find that the flavour symmetry breaking effects should be carefully considered for $B_{u,d,s}$ decays, and suggest that 