Let's talk about knowledge related to PHP7+ expanded type conversion

With the development of the PHP language, PHP7 has been greatly improved in performance and security. Among them, the expanded type conversion function is a very practical function, which can make the code more concise and efficient. This article will introduce the relevant knowledge of PHP7 extended type conversion.

1. Overview

Extended type conversion refers to converting one data type into another data type. Before PHP7, we usually used a series of functions to convert data types, such as intval(), floatval(), strval(), boolval(), etc. However, there are still some problems with these functions:

1. Function names are not easy to remember;
2. Functions sometimes cause code verbosity and readability problems;
3. Function calls sometimes cause strange errors.

In order to solve these problems, PHP7 introduces the extended type conversion function, which can perform type conversion through new syntactic sugar.

2. Basic Usage

In PHP7, we can use the following syntactic sugar for type conversion:

1. (int) $var: Convert $var to Integer type;
2. (float) $var: Convert $var to floating point type;
3. (string) $var: Convert $var to string type;
4. (bool) $var: Convert $var to Boolean value.

The following are some examples of using syntax sugar for type conversion:

<?php
    $a = "123";
    $b = (int) $a;
    echo gettype($b); // 输出：integer
    
    $c = 3.14;
    $d = (string) $c;
    echo gettype($d); // 输出：string
    
    $e = "true";
    $f = (bool) $e;
    echo gettype($f); // 输出：boolean
?>

As a dynamic language, PHP's data type is determined at runtime, so these extended type conversions Syntactic sugar can be very useful in the right circumstances. This section provides some simple examples to illustrate this point.

3. In-depth study

In PHP7, the expanded type conversion function can not only convert basic data types, but also convert some special data types.

1. Array conversion

When we need to convert an array into a string, using the implode() function is still a good choice. But it can also be achieved using the extended type conversion function:

<?php
    $arr = array("hello", "world");
    $str1 = implode(&#39;,&#39;, $arr);
    $str2 = (string) $arr;
    echo $str1."n".$str2;
?>

Output result:

hello,world
Array

When using extended type conversion syntax sugar to convert an array into a string, the output result is Array, which is not what we want. The solution to this problem is to use the __toString() function, which converts the array into an object.

<?php
    class A {
        private $arr = array("hello", "world");
        public function __toString() {
            return implode(&#39;,&#39;, $this->arr);
        }
    }
    $a = new A();
    echo (string) $a;
?>

Output result:

hello,world

2. Object conversion

In addition to arrays, we can also convert objects into different types by using extended type conversion syntax sugar type of data. Here are a few examples:

<?php
    class Test {
        private $var = "hello,world";
        public function __toString() {
            return $this->var;
        }
        public function __toInt() {
            return (int) $this->var;
        }
        public function __toFloat() {
            return (float) $this->var;
        }
        public function __toArray() {
            return array($this->var);
        }
    }
    $t = new Test();
    echo (string) $t; // 输出：hello,world
    echo (int) $t; // 输出：0
    echo (float) $t; // 输出：0
    print_r((array) $t); // 输出：Array ( [0] => hello,world )
?>

First of all, if we look at the above example, we will find that four methods __toString(), __toInt(), __toFloat(), and __toArray() are defined in the Test class. These methods are the core of extending the type conversion function, so we must define them to implement new data type conversion methods.

In the above code, when we convert the Test object to a string type, the __toString() method will be automatically called and the corresponding string will be returned. Similarly, when an object is converted to an integer or floating point type, the __toInt() or __toFloat() method is automatically called for conversion. When an object is converted to an array type, the __toArray() method is automatically called.

When using extended type conversion, pay special attention to the order of type conversion. For example, if we call (int) $t, but $t does not define the __toInt() method, the __toString() method is automatically called. And if the __toString() method is not defined, 0 will be returned.

4. Summary

Extended type conversion is a very practical new feature of PHP7, which can make the code more concise and efficient. When using extended type conversion, you need to pay attention to the type conversion order and the implementation of the type conversion method. In addition, extended type conversion can also be extended to self-defined data types, bringing more convenience to our code development.

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