How to use parameters of PHP functions?

Function parameters allow data to be passed to the function. There are two transfer methods: Pass by value: The original variable is not affected by function modification. Pass by reference (starting with ampersand): Function modifications affect the original variable. Practical case: In form validation, fields passed by value will not be modified, but error arrays passed by reference can be modified outside the function.

How to use parameters of PHP functions

Introduction

Function parameters allow you Pass data to the function when it is called. Functions can get parameters in the following ways:

• Pass by value: The value of the parameter is copied into the function. Any changes to the function will not affect the original variable.
• Pass by reference: The reference of the parameter is passed into the function. Changes made by the function to the parameters also affect the original variables.

Pass by value

By default, parameters are passed by value. This means that any changes made to the parameters inside the function will not affect the original variables.

Example:

function increment($value) {
    $value++;
}

$number = 10;
increment($number);

echo $number; // 输出：10

Even if we try to increment the value of $number using the increment() function, the original variable$number remains unchanged.

Pass by reference

To pass a parameter by reference, use the & symbol before the parameter. This will allow the function to access the original variable directly.

Example:

function incrementByReference(&$value) {
    $value++;
}

$number = 10;
incrementByReference($number);

echo $number; // 输出：11

Now, changes made to $number by the incrementByReference() function are also reflected in the original in variables.

Practical case

Form validation

function validateForm($data) {
    // 按值传递
    $name = $data['name'];
    $email = $data['email'];

    if (empty($name)) {
        // 按引用传递，可以在函数外部修改
        $data['errors'][] = '名称不能为空';
    }

    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $data['errors'][] = '无效的电子邮件地址';
    }
}

In the above example, $name and $email are passed by value, so any changes to them will not affect the original data. However, the $errors array is passed by reference and therefore can be modified from outside the function.

Function signature

It is very important to specify the method of passing parameters in the function signature:

• Pass by value: type variable name
• Pass by reference: &Type variable name

Conclusion

By understanding how to use function parameters, you can more Effectively write reusable and maintainable code.

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