PHP type prompts to improve code quality by clarifying parameters and return value types. 1. The parameter type prompt uses basic types such as string or class names to restrict parameters to avoid illegal types being passed; 2. The return value type prompt ensures that the function returns the expected type, and enables strict mode with strict\_types; 3. The null type can be used?User supports null return but should be used reasonably; 4. The PHP8 joint type uses | declares multiple types compatible such as float|int to enhance expression.
PHP's Type Hinting is a very practical feature in modern PHP development. It helps developers explicitly specify the types of variables in functions, method parameters and return values. This not only improves the readability and robustness of the code, but also reduces potential errors.
Let’s take a look at the basic syntax of PHP type prompts and some things to pay attention to based on several common usage scenarios.
1. Parameter type prompt: Make the argument transmission clearer
PHP supports writing type names directly into parameters of functions or methods. For example:
function saysHello(string $name): void {
echo "Hello, $name";
} string $name here is the parameter type prompt. If the passed in is not a string, such as a number or an array, a TypeError will be thrown.
- Common basic types include:
string,int,float,bool - You can use the class name as a type prompt, such as
\DateTime $date - Interfaces and abstract classes can also be used as type prompts for dependency injection and other scenarios.
Note: By default, PHP does not automatically convert types. For example, if you pass a string "123" to an int parameter, it will not automatically be converted into an integer, but will report an error.
2. Return value type prompt: know what the function should return
In addition to parameters, you can also add a return type after a function or method:
function getAge(): int {
return 25;
} This : int means that this function must return an integer. If you accidentally return a string or null, an error will be reported during runtime.
- Common types include basic data types and object types
- If the function does not return a value, it is recommended to use
voidto express it explicitly - If the function may return multiple types, you can use
mixed(but not recommended)
Tips: Turn on strict mode during development ( declare(strict_types=1); ) to make parameter type checking stricter and avoid unexpected type conversion.
3. Nullable Types: The situation where null is allowed to be returned
Sometimes you need to allow a parameter or return value to null. At this time, you can use the nullable type, that is, add a question mark before the type:
function findUser(int $id): ?User {
// The user may not be found return null;
} Here ?User means either returns a User object or returns null.
- Can be used for parameters and return values
- Basic types also support nullability, such as
?string - Be careful not to abuse it, null should be a reasonable "not found" state, not an error handling method
4. Union Types: suitable for multiple types
PHP 8 introduces union types, you can use vertical bar | to represent that a variable can be one of multiple types:
function formatValue(float|int $value): string {
return number_format($value);
} Here $value can be float or int.
- Suitable for parameters, return values and even attributes
- Avoid
mixed, and when you do know several possible types, use union types to be clearer - Note the order issue: Some IDEs and tools may have requirements for type order
Basically that's it. The type prompt function of PHP is quite complete, and reasonable use can make the code clearer and easier to maintain. Although it may feel a little restrictive at first, it is a good habit worth investing in the long run.
The above is the detailed content of Understanding PHP Type Hinting Syntax. For more information, please follow other related articles on the PHP Chinese website!
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