This article mainly introduces the usage skills of each and list functions in PHP. Interested friends can refer to it. I hope it will be helpful to everyone.
1. Usage of each
Let’s look at the API first
array each (array &$array)
This is described in the api: each - returns the current key/value pair in the array and moves the array pointer forward one step
Let's first take a look at what the returned array looks like Like?
<?php $arr = array('你','若','安','好','便','是','晴','天'); print_r(each($arr)); print_r(each($arr)); echo '<hr />'; /* 返回 Array ( [1] => 你 [value] => 你 [0] => 0 [key] => 0 ) Array ( [1] => 若 [value] => 若 [0] => 1 [key] => 1 ) */ //执行相同的一段代码,从‘你'到‘若',说明each是会每执行一次,游标向数组尾部移动一步 //0和Key存放的是键 //1和value存放的是值 //因此each满足遍历数组的,得到当前的键和值,以及每执行一次,向尾部移动一步游标 //因此循环数组也可以用each这么写 reset($arr); for(;$tmp=each($arr);){ echo $tmp[0],'~',$tmp[1],'<br />'; } /* 返回 0~你 1~若 2~安 3~好 4~便 5~是 6~晴 7~天 */ ?>
2. How to use list
Let’s first look at what the api says
Like array(), this Not really functions, but language constructs. list() uses one step to assign values to a set of variables.
Let’s look at an example:
<?php list($a,$b)=array(10,20); echo $a,'~',$b,'<br />'; //返回10~20 ?>
Yes, you can assign values to a set of variables
Let’s look at another example:
<?php list($a,$b,,$c)=array(2=>10,3=>20,4=>30,1=>40); echo $a,'~',$b,'~',$c,'<br />'; //返回notice~40~20 //执行到$a的时候返回给我一个notice:说数组没有0键 ?>
According to the general idea, it should Will return: 10~20~40
Why will this notice~40~20 be returned?
Answer: This involves the operating mechanism of the list. This is how the list is assigned
First of all: ignore the array on the right and look at the variables in the List. From left to right it should be $a = arr[0] $b=arr[1] $c=arr[3]
Then: start assigning values from right to left, the order of assignment is $c=arr[3] $b=arr[1 ] $a=arr[0]
So $c=20 $b = 40 Because there is no arr[0], $a gave a warning
3 .Use each and list to implement array traversal
<?php $arr = array('你','若','安','好','便','是','晴','天'); for(;list($k,$v)=each($arr);){ echo $k,'~',$v,'<br />'; } /* return: 0~你 1~若 2~安 3~好 4~便 5~是 6~晴 7~天 */ ?>
Summary: The above is the entire content of this article, I hope it can be helpful to everyone Learning helps.
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php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

在php中,可以使用substr()函数来读取字符串后几个字符,只需要将该函数的第二个参数设置为负值,第三个参数省略即可;语法为“substr(字符串,-n)”,表示读取从字符串结尾处向前数第n个字符开始,直到字符串结尾的全部字符。

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\ \;||\xc2\xa0)/","其他字符",$str)”语句。

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。


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