Basic tutorial for getting started with php - PHP array

This section introduces PHP arrays to you. Arrays are very important in PHP programming and are used in many places. It is recommended that you master them well.

1. Array definition:

<?php
$arr[0] =1;
$arr[1] ="hello";
$arr[3] =2.5;

[0]: represents the subscript of the array, or is called a keyword $arr[0]: represents an element of the array $arr[0] =1: 1 represents the value of the array $arr: represents the name of the array

Example 1,

<?php
/**
* 定义数组
* site bbs.it-home.org
*/
$arr[0] =1;
$arr[1] ="hello";
$arr[2] =2.5;
$arr[3] =true;
$arr[4] =null; //即使放入一个空，也要占用一个空间

echo '总共有'.count($arr).'个数组元素<br/>'; //函数count 计算出有多少个元素

//遍历数组
for($i =0;$i<count($arr);$i++){
echo '第'.($i+1)."个是".$arr[$i].'<br/>';
}
?>

Example 2,

<?php
/**
 * 数组遍历
*/
$arr["logo"] = "北京";
$arr["pwm"] = 123;
$arr[123] ="abc";

//遍历
/*
for($i=0;$i<count($arr);$i++){
echo $arr[$i];
}*/
//foreach遍历适用范围更广
//by bbs.it-home.org
foreach($arr as $key=>$val){
   echo $key.'='.$val.'<br/>';
}

Results: logo=Beijing pwm=123 123=abc

Note: 1. //************Special instructions

<?php
$arr = array(5=>"logo",45,70,); //没有给数组定义下表，PHP就会自动用前面最大的数作为第一个下标，后面的元素下标自动加1
//访问logo这个数组的值我们可以这样写
//$arr[5] = "yes"; 会替换元素的值
echo $arr[5].'<br />';
echo $arr[7];
//by bbs.it-home.org

2. //Use decimal as key, and the PHP system automatically truncates the decimal part

<?php
$a = array('abc'=>12,'ppp'=>234,12.7=>"world");
print_r($a);

Result: Array ([abc] => 12 [ppp] => 234 [12] => world )

3. Use true false null as keyword (subscript)

<?php
//使用true false null 作为关键字（下标）
$a[true] ="what";  //等价于$a[1]
$a[false] ="hahaa";  //等价于$a[0]
$a[null] ="中国";  //等价于$a[null] 或者$a[""]
//这样输出
echo $a[0].'<br/>';
echo $a[null].'<br/>';

$a[22.6]=133; //使用小数作为key，PHP系统自动截断小数部分

//用print_r来输出数组来显示数组的情况
print_r($a);
echo '<br/>';
//用var_dump更详细显示数组的信息
var_dump($a);

Effect: hahaa China Array ( [1] => what [0] => hahaa [] => China [22] => 133 ) array(4) { [1]=> string(4) "what" [0]=> string(5) "hahaa" [""]=> string(6) "China" [22]=> int(133 ) }

4. PHP arrays can dynamically and automatically grow

<?php
//PHP数组可以动态自动增长
$a = array(3,4);
$a[3] =4;
//echo $a[2];  //引用的数组（数组元素）不存在，系统就会报错
print_r($a);

5. Several important functions in arrays

<?php
$a=array(1,2,3,"one","two","three");
echo count($a).'<br/>'; //统计函数的元素个数
echo is_array($a).'<br/>'; //判断是否是一个数组
print_r($a);
echo '<br/>';
var_dump($a); //显示数组信息

$b="1 2 3 'one' 'two' 'three'";
echo '<br/>-------------------------';
print_r(explode(" ",$b));

$b =array();
echo count($b);
?>

Thank you for paying attention to the PHP introductory tutorials. This series of PHP basic tutorials will help PHP newbies quickly master the PHP programming language. Programmer's Home will continue to launch PHP-related tutorials for everyone, and I wish you all the best in your learning and progress!