php query all data types

PHP is a widely used server-side scripting language that, like other programming languages, supports a variety of data types. This article will introduce data types in PHP and their mutual conversion.

1. Integer type

In PHP, the integer type represents an integer, which can be expressed in decimal, octal or hexadecimal. For example:

$a = 123;        // 十进制
$b = -456;       // 负数
$c = 0123;       // 八进制
$d = 0x1A;       // 十六进制

2. Floating point type

The floating point type represents a decimal, which can be written in regular mathematical form or scientific notation. For example:

$a = 1.234;
$b = 3.14E-2;
$c = 7E3;

3. String type

The string type consists of a string of characters enclosed in single quotes or double quotes. For example:

$a = 'hello, world!';
$b = "hello, $name!";

4. Boolean type

Boolean type represents true or false, which can be expressed as true or false. For example:

$a = true;
$b = false;

5. Array type

The array type represents an ordered list of one or more values, represented as a comma-separated list between square brackets, or Created using the array() function. For example:

$a = array(1, 2, 3);
$b = [4, 5, 6];

6. Object type

Object type is an instance of a custom data type. You can create an object using the new keyword, or use an already instantiated object. For example:

class Person {
    public $name;
    public $age;
}
$p = new Person();
$p->name = 'Tom';
$p->age = 20;

7. Null type

Null type means there is no value, only one value, null. For example:

$a = null;

8. Resource type

A resource is a reference to an external resource such as a database or file handle. For example:

$fp = fopen("file.txt", "w");

The above are all the basic data types in PHP. We can also convert data types through type conversion functions. For example:

// 把字符串转换为整型
$a = '123';
$b = (int)$a;

// 把整数转换为字符串
$b = 456;
$d = (string)$b;

In general, PHP supports various data types, which we can choose and use according to different development needs. At the same time, in PHP, data type conversion is also an important part. During the actual development process, we must pay attention to the conversion between data types to avoid unexpected type errors.

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