What are the basic data methods for variables in php

One way to store data in php is the amount that i can change. This method is to open up a space in the memory that can store data, and give this space a name, the space at this time can be called a variable. This value can be changed during operation

The name of the current space is the variable name, and the data (eight data types) of the current space is called the variable value

Definition Variables and assign values (recommended learning: PHP video tutorial)

Define variables: $variable name; Note that variables defined in this way are OK, but cannot be used, and an error will be reported if output directly , must be followed by a variable value before it can be used

notice: Note

undefined: undefined

variable: variable

Define variables and assign values: $ Variable name = variable value;

<?php// $a;// echo $a;$a =1;echo $a;?>

Rules for defining variables

Variable names are case-sensitive

Variable name It is recommended to use meaningful names. When you see the variable name, you will know what it means, such as $name, $age, $sex, $get_user_name

Naming rules: it must be composed of numbers, letters, and underscores and cannot start with Start with numbers. For example: $a1, $A1, $a_1, $_a1, $_2 are all acceptable but cannot be $1a.

Three naming rules:

Camel case naming method: the first letter of the first list is lowercase, and the other letters are uppercase. For example, $getUserName

underscore nomenclature: each word is separated by an underscore. For example, $get_user_name

Pascal nomenclature: the first letter of each word is capitalized. For example: $GetUserName

Several commonly used functions for variables:

echo: Print the value of the variable

var_dump(): Print the type of the variable , length, value

isset(): Determine whether the variable exists. If the variable exists and is not null, it returns true, otherwise it returns false

unset(): Destroy the variable

Eight data types of variables

Scalar types: int (integer type), float (floating point type), boolean (Boolean type), string (string type)

Composite types: array (array), object (object)

Special types: null (empty), resource (resource)

int: integer type

Integer types include positive integers, negative integers and 0. Just write numbers directly when defining variable assignments

float: floating point type

Description: Including decimals, negative decimals, positive decimals and 0.0

string: String type

Description: As long as it is any type of data plus single quotes or Double quotes are the string type,

boolean: Boolean type

Description: The Boolean type has only two values, true and false, and the Boolean value is combined with some other methods For example, use process control

array array

Description: An array is a special variable that can store multiple values ​​in a single variable

object object

Empty type

Description: A way to define an assignment to a variable without any value

resource resource

Note: It is not a specific value, but a collective name for a variety of data

The above is the detailed content of What are the basic data methods for variables in php. For more information, please follow other related articles on the PHP Chinese website!