Arrays for Beginners to PHP

1. An array can store multiple values ​​in a single variable

<?php
	header("Content-type: text/html; charset=utf-8");//设置编码 
	$arr = array('one','two','three','four','five');
?>

2. What is an array

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

Arrays can store multiple values ​​in a single variable, and the values ​​can be accessed based on keys

3. How to create an array in php

array () Function is used to create arrays

4. There are 3 arrays in php

(1). Arrays with numeric ID keys----numeric arrays

(2). Array with specified keys, each key is associated with a value -------Associative array

(3). Array containing one or more arrays---- ----Multidimensional array

Numeric array

<?php
	$cars=array("Volvo","BMW","Toyota");  //创建一个名为 $cars 的数值数组，并给数组分配三个元素
	echo "I like " . $cars[0] . ", " . $cars[1] . " and " . $cars[2] . "."; 
?>

Associative array

Associative array is an array using the specified key that you assign to the array

<?php
	$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
	echo "Peter is " . $age['Peter'] . " years old.";
?>

Traverse the association Array

<?php
	$age=array("Peter"=>"35","Ben"=>"37","Joe"=>"43");
	//是使用foreach 遍历关联数组
	foreach($age as $x=>$x_value){
		echo "Key=" . $x . ", Value=" . $x_value;
		echo "<br>";
	}
?>

Traverse and print all values ​​in the associative array

Multidimensional array

<?php
	$arr = array(
			        array(
					"www.taobao.com",
					"www.baidu.com"
				     ),
				array(
					"www.php.cn",
					"www.tianmao.com"
				     )
			);
		print('<pre>');
		print_r($arr);
		print('</pre>');
?>

Get the array length----------count() function

In the following case, get the length of an array

<?php
	$arr = array(1,2,3,4,5,6,7,8,9);
	echo count($arr);
?>

Array sorting

Array sorting, There are functions for sorting arrays in php

1.sort() - Sort the array in ascending order

2.rsort() - Sort the array in descending order

3 .asort() - Sort the array in ascending order based on the value of the associative array

4.ksort() - Sort the array in ascending order based on the keys of the associative array

5.arsort() - Sort the array in descending order according to the value of the associative array

6.krsort() - Sort the array in descending order according to the key of the associative array

sort()

<?php
	//升序
	$arr = array(1,15,6,8,1,28,35,26,7);
	sort($arr);
	echo "<pre>";
	print_r($arr);
	echo "</pre>";
?>

##rsort()

<?php
	//降序
	$arr1 = array(1,15,6,8,28,35,26,7);
	rsort($arr1);
	echo "<pre>";
	print_r($arr1);
	echo "</pre>";
?>

##asort()

<?php
	//asort
	$arr = array('a','b','c');
	asort($arr);
	echo "<pre>";
	print_r($arr);
	echo "</pre>";
?>

arsort()

<?php
	//arsort
	$arr = array('a','b','c');
	arsort($arr);
	echo "<pre>";
	print_r($arr);
	echo "</pre>";
?>

ksort()

<?php
	//ksort
	$arr = array('a'=>10,'b'=>5,'c'=>20);
	ksort($arr);
	echo "<pre>";
	print_r($arr);
	echo "</pre>";
?>

krsort()

<?php
	//krsort
	$arr = array('a'=>10,'b'=>5,'c'=>20);
	krsort($arr);
	echo "<pre>";
	print_r($arr);
	echo "</pre>";
?>