How many data types are there in php array

The data types in the php array are divided into three categories: scalar type, composite type and special type. The eight subcategories are: 1. boolean, Boolean type; 2. integer, integer type; 3. float, Floating point type, also called double; 4. string, string; 5. array, array; 6. object, object; 7. resource, resource type; 8. NULL, empty null.

The operating system for this tutorial: Windows 10 system, PHP8.1.3 version, Dell G3 computer.

PHP’s data types are divided into three major categories and eight subcategories:

1. Scalar type

boolean (Boolean type) : This is the simplest type, with only two values, which can be TRUE/true or FALSE/false, and are not case-sensitive. For details, please see: PHP Boolean type (boolean)

integer (integer) : Integer values ​​can be expressed in decimal, hexadecimal or octal, and can be preceded by optional symbol (- or). Octal represents a number that must be preceded by 0 (zero), and hexadecimal represents a number that must be preceded by 0x. For details, please see: PHP integer data (integer)

float (floating point type, also called double) : For details, please see: PHP floating point type (float)

string(string): Unlike other programming languages, character variables are divided into characters and strings. In PHP, character variables are uniformly used to define characters or strings. For details, please see: PHP string type (string)

2, composite type

array (array) : Array type variable is a Special variable types

object (object): Object is also a special data type. To create an object variable, you generally use the new keyword to obtain it. For details, please see: PHP object Type (object)

3. Special type

resource (resource type) : Resource is a special variable that is saved externally A reference to the resource. Resources are created and used through specialized functions. For details, please see: PHP resource type (resource)

NULL (empty null) : Indicates that a variable has no value. The only possible value of NULl is NULL

Note: PHP is a weakly typed language, its variables have no data type, but the data stored in the variable has a corresponding data type

integer data Type: uses 8 bytes to store, and provides a variety of integer storage methods

$num = 10;           // 十进制

   $num1 = 0123;        // 八进制（83）

   $num2 = 0x123;      // 十六进制（291）

   $num3 = 0b1101;     //二进制（13）

Floating point data type: uses 8 bytes to store, and provides a variety of storage methods

$float_num = 1.23;

   $float_num1 = 1.23e3;       // 1.23乘10的3次方

The way it is stored in memory is: part of the 8 bytes is used to store the exponent, and part of it is used to store significant digits. Sometimes, when it exceeds a certain range, the accuracy will be lost.

String data type

In PHP, all data entered by the user and data defined by the programmer using quotation marks (single quotation marks and double quotation marks) are understood by the system as strings, PHP7 The length of a string is theoretically unlimited

Both single quotes and double quotes can define strings, but they are different from each other:

--Only a small number of escapes can be parsed in single quotes Symbols: \', \

--Double quotes can parse more escape characters: $, \", \n

Double quotes can parse nested characters in strings PHP variables (variables should be separated from other strings, use {})

$a = "你好";

    $c = "$a世界";

    // $c = "{$a}世界" 常用

    echo $c;        //输出“你好世界”

String View

You can view the string specified by the subscript $str[1] When the index is a negative number, the subscript character is used as the index direction from back to front

Define the array

Arrays can be defined in many ways in PHP. The common ways are as follows ：

-- Use the array keyword to initialize the array

-- Use the array brackets [ ] to initialize the array

// 使用array

   $arr1 = array();        // 可以不指定元素

   $arr2 = array("name", "age");

// 使用[]定义数组

   $arr3 = [];

   $arr4 = ["name", "age"];

Characteristics of arrays

1. Theoretically there is no limit on the number of elements in a PHP array

2. Elements can be dynamically added to a PHP array

3. The value of a PHP array element can be of any data type

4. PHP array subscripts can be pure numbers (index array), pure strings (associative arrays), mixed numbers and strings (mixed arrays)

Type judgment

Determine the data type through system functions: the format of the function starts with is_, followed by the corresponding data type, and the return result is a Boolean type.

Type conversion

Automatic conversion: PHP will automatically convert data of unqualified data types into target type data according to the computing scenario in which the data will participate. This conversion will not change the original data type of the variable

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