PHP's data types fall into three groups: scalar types that hold one value, compound types that hold several, and special types.
Scalar: bool for true or false, int and float for numbers, and string for text. A float is also called a double.
Compound: array, object and callable. iterable is a type alias for an array or a Traversable object.
Special: null for no value, and resource for a handle such as a file.
PHP is dynamically typed. A variable takes its type from its value and can change type while the script runs. Type declarations add checks where you want them.
Rewriting in plainer words…
This answer doesn't lend itself to a diagram - it reads best . No credits were charged.
