Detailed explanation of type hint function in PHP

This article mainly introduces the type hinting function in PHP. This article explains the function, usage and usage examples of type hinting. I hope to be helpful.

Overview

Starting from PHP5, we can use type hints to specify the parameter types that the function receives when defining the function. If the parameter type is specified when defining a function, then when we call the function, if the type of the actual parameter does not match the specified type, PHP will generate a fatal error (Catchable fatal error).

Class names and arrays

When defining functions, PHP only supports two type declarations: class names and arrays. Class name table name The actual parameter received by this parameter is the object instantiated by the corresponding class, and the array indicates that the actual parameter received is an array type. The following is an example:

function demo(array $options){
  var_dump($options);
}

When defining the demo() function, the parameter type received by the function is specified as an array. If when we call a function, the parameter passed in is not an array type, for example, a call like the following:

$options='options';
demo($options);

Then the following error will occur:

Catchable fatal error: Argument 1 passed to demo() must be of the type array, string given,

You can use null as the default parameter

Note

One thing that needs special attention is that PHP only supports two types of type declarations. Any declaration of scalar types is not supported. For example, the following code will generate an error:

function demo(string $str){
}
$str="hello";
demo($str)

When we run the above code, string will be treated as a class name, so a report will be reported. The following error:

Catchable fatal error: Argument 1 passed to demo() must be an instance of string, string given,

Summary

Type declaration is also an improvement in object-oriented PHP, especially when catching exceptions of a specified type. it works.
Using type declarations can also increase the readability of the code.
However, since PHP is a weakly typed language, using type declarations is contrary to the original intention of PHP design.
Whether to use type declarations or not is a matter of opinion.

Related recommendations:

PHP type conversion function intval_PHP tutorial

php type constraints

php type operator instanceof

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