1-1 PHP compilation features

1-2 The underlying implementation of variables

1-3 Implementation of variable types

1-4 symbol table roster of variables

1-5 What happens to assignment by value?

1-6 cow copy-on-write feature

1-7 What happens to reference assignment

1-8 forced division

1-9 Weird behavior when referencing arrays

1-10 Strange phenomenon when looping array_all

1-11 Symbol table and scope

1-12 Implementation of static variables

1-13 constant

1-14 object

1-15 memory tiering