Is php a strongly typed language?

PHP is a weakly typed language

We note that it is not necessary to declare the data type of the variable to PHP.

PHP will automatically convert the variable into the correct data type based on its value. In a strongly typed programming language, we must declare (define) the type and name of the variable before using it.

1. First define some basic concepts

Program Errors

trapped errors. Causes the program to terminate execution, such as division by 0, array out-of-bounds access untrapped errors in Java. Execution continues after an error, but arbitrary behavior may occur. For example, buffer overflow in C, Jump to error address

Forbidden Behaviors

When designing a language, you can define a set of forbidden behaviors. It must include all untrapped errors, But it may contain trapped errors.

Well behaved, ill behaved

well behaved: If forbidden behaviors are not possible during program execution, it is well behaved.

ill behaved: Otherwise, it is ill behaved...

2. With the above concepts, let’s discuss strong and weak types, static and dynamic types

Strong and weak types

strongly typed: If all programs in a language are well behaved - that is, forbidden behaviors are impossible, then the language is strongly typed.

Weak type weakly typed: Otherwise, it is weakly typed. For example, buffer overflow in C language belongs to trapped errors, that is, forbidden behaviors. Therefore, C is a weakly typed person. As the previous people have also said, weakly typed languages ​​have less strict type checking, such as preferring to tolerate implicit type conversions. For example, int in C language can be turned into double. The result is: it is easy to produce forbidden behaviors, so it is weakly typed

dynamic, static type

static type statically: If an ill-behaved program is rejected at compile time, it is statically typed;

dynamic type dynamiclly: If ill behaviors are rejected at runtime, it is dynamically typed.

3. Misunderstanding
Everyone thinks that C language needs to write int a, int b and the like, but Python does not need to write (you can write a, b directly), so C is static. Python is dynamic. This understanding is not accurate enough. For example, Ocaml is statically typed, but it doesn't need to be written explicitly. Ocaml is a static implicit type

Static types can be divided into two types:
If the type is part of the language grammar, it is an explicitly typed explicit type; if the type is compiled Derivation is implicit typed implicit type, such as ML and Haskell
4. Here are some examples
No type: Assembly
Weak type, static type: C/C
Weak type, dynamic type checking: Perl/PHP
Strong type, static type checking: Java/C
#Strong type, dynamic type checking: Python, Scheme
static Explicit type: Java/C
static Implicit types: Ocaml, Haskell

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