PHP was created by Rasmus Lerdorf in 1994, although an enormous group of people followed him who contributed their knowledge to the programming language. Between them, they developed a classic programming language with variables, sentence conditions, loops, etc.
The manual is written in very simple language so everyone can understand it. It is also accompanied by many images so the concepts are more clear.
It is without a doubt a great way to acquire basic PHP knowledge and to start getting into the topic.