20141225 Array One

Review

Custom functions: Return values, parameter passing values (value passing and reference passing), scope (global and local, Hyper Global), static variables (function counter: static variable = value;).

anonymous function: Variable + ()

Pseudo type: Tells the user the type of the current data

Variable functions: Access through variable constructors

Data type judgment: Is_ data type

Data type conversions: Casts and auto-conversions, Settype and GetType

File contains: HTML layout and code reuse (multiplexing), include and require, path (absolute path and relative path)

Common system Functions

String functions, mathematical functions, time-date functions

String Functions

Strlen: Get string length, byte length

Bytes: Refers to the computer's storage unit, one byte = 8 bits

Characters: graphical symbols that are visible to the user, characters converted into bytes by character set

GBK: one character = 2 bytes

UTF-8: usually one character = 3 bytes, Special one character = 2/4 bytes

SUBSTR: String intercept, get string (intercept by byte)

String substr (target string, starting position of string [, intercept length])

The first letter of all strings in PHP occupies a position of 0

Strtolower: All characters are lowercase (for the English alphabet)

Strtoupper: All characters are capitalized

Strrev: String inversion (can only reverse English: only one byte in English storage), reverse by byte

Strpos: Find the position of the corresponding character (digital subscript) from the string, and start at the far left

Strrpos: As with Strpos, just start looking from the right side of the string

Commonly used with string interception (SUBSTR)

STRCHR: Similar to substr, intercept from a specified position until the last

STRRCHR (get file suffix name): As with STRCHR, just start looking for characters from the right

Trim: Remove the characters from both sides of the function by default, which removes contiguous content from both sides, not across content

String Trim (target string [, List of strings to be removed])

Typically: trim is used to exclude spaces or a specified character

Time-Date function

Time-date functions in PHP are powerful

Time: Gets the timestamp of the current time (int: Starting from GMT January 1, 1970 0:0 0 seconds) Number of seconds

Date: Time-serialization function that converts the specified timestamp to the display format of a given time date (random string: A professional format specifier), and if no timestamp is specified, the system uses the timestamp of the current time by default

Strtotime: The time-date format string is converted to the corresponding timestamp (as long as the correct English time expression can be converted)

Microtime: microsecond timestamp, returning different results according to different requirements

Mixed Microtime (Boolean type), can return the time of a floating-point number, or it can return an array (timestamp and microseconds)

Math-related functions

ABS: Absolute Value

Floor: Rounding Down

Ceil: Rounding up

Round: Rounding

Rand: Gets a random integer within the specified range

Mt_rand: Gets a random integer within a specified range (more efficient)

Array Basic Concepts

1. What is an array?

A collection of data, where multiple information is saved by a variable.

2. Features of PHP arrays

A) There is no data type limit for data in PHP arrays

b) PHP array has no data length limit (data length, array element length)

c) The subscript of a PHP array element can be a number or a string

array Syntax Defining Arrays

Mode 1:

Variable = array (); Empty array

Variable = array (1,2,3,4,5); Array inner elements are delimited with commas

Mode 2:

variable = [1,2,3,4,5];

Mode 3:

Variable [] = value;

Adding an array element

All array elements are added by using [] in the form of an array variable (dynamically added)

Array variable [] = value; Add an element to an array variable

Mode 1: The system automatically increases the subscript of the element: Key Name

Array variable [] = value

Method 2: Manually increment the subscript of the element: Key Name (value)

Method 3: Manually add the element subscript: string

Array Access

All arrays are accessed in the same way: they are accessed through the subscript of the array element

Syntax: variable name [' Subscript ']

PHP Array Classification

PHP Array classification based on: array subscript

Divided into three categories: indexed arrays, associative arrays, mixed arrays

Indexed array: The subscript of all array elements is all numbers

Associative arrays: The subscripts of all array elements are strings

Mixed arrays: Array subscripts have both numbers and strings

In PHP: Array subscript is unique, PHP subscript if the string is case-sensitive.

iterating through an array

Take out all the elements in the array

For Loop

Satisfy the basic condition: know the length of the array; the subscript of an array must be an index and increment from 0.

foreach Loop

The Foreach loop is designed to iterate through the elements of an array, taking the key names and values of the current array elements out and assigning them to the corresponding variables, respectively.

Syntax: foreach (array variable as [key name variable =>] Value variable) {

Use key name variables and value variables to output array element data corresponding to the operation

}

20141225 Array One