How does someone pray who has one leg and leans on a wall? Is his prayer valid?

Standing in obligatory prayers is a pillar for one who is able to do so. If a person has one leg and is able to stand on it, then standing is obligatory for them, unless they experience severe hardship. The criterion for hardship that exempts one from standing is that which removes khushu' (devotion) and presence of heart, or if it is so severe that it causes extreme fatigue or dizziness preventing them from standing. The worshipper must pray standing, even if leaning on a cane or a wall, if they are able to do so. If one prays leaning while being able to stand independently, then if the leaning is slight, the prayer is valid but disliked. However, if the leaning is strong, such that they would fall if what they are leaning on were removed, then there is a difference of opinion among scholars regarding the prayer's validity. The Shafi'is hold that the prayer is valid but disliked, while the Malikis hold it to be invalid if done intentionally and not out of ignorance.