In PHP, it is very simple for us to sort one-dimensional arrays. We only need to use sort(), rsort() and it is done. If we want to sort multi-dimensional data, PHP does not have such a function, so we need it. Did it myself.
For php array sorting PHP provides a lot of functions. I will list them below. If not, you can add them.
The sort() function is used to sort array cells from low to high.
The rsort() function is used to sort array cells from high to low.
The asort() function is used to sort the array cells from low to high and maintain the index relationship.
The arsort() function is used to sort the array cells from high to low and maintain the index relationship.
The ksort() function is used to sort array cells from low to high by key name.
The krsort() function is used to sort array cells from high to low by key name.
But today we are mainly talking about the array sorting function that comes with PHP, mainly about custom sorting
1. Bubble sorting method
Description: Find the largest number, arrange it to the end, and then continue to find
Example:
The code is as follows | Copy code | ||||
$arr = array(3,5,- 1,0,2);
$temp = $arr[$j]; $arr[$j]=$arr[$j+1]; $arr[$j+1]=$temp; } } } |
Understanding:
3, 5, -1, 0, 2
//Start from the first number and compare backwards. If it is larger than the following number, adjust the position with the following number
//The first time, 3 is less than 5, then it remains unchanged
//The second time, 5 is greater than -1, then it becomes
3, -1, 5, 0, 2
//The third time, 5 is greater than 0
3, -1, 0, 5, 2
//The fourth time, 5 is greater than 2
3, -1, 0, 2, 5
This completes an inner loop. At this time, the last number is sorted and will not participate next time 3, -1, 0, 2, 5 The second outer loop begins. The first time: 3 is greater than -1
代码如下 | 复制代码 |
$arr=array(2,1,-1,3,0); for($i=0;$i $minindex = $i; for($j=1+$i;$j $minindex = $j; } } $temp = $arr[$i]; $arr[$i] = $arr[$minindex]; $arr[$minindex] = $temp; } |
The code is as follows | Copy code |
$arr=array(2,1,- 1,3,0);
for($i=0;$i |
Understanding:
2, 1, -1, 3, 0
//Assume that the first number 2 is the minimum value, and the subsequent numbers are compared with 2 in turn to find the smallest number
Process:
1 is less than 2, then minval=1
-1 is less than 1, then minval=-1
3 is greater than -1, unchanged
0 is greater than -1, unchanged
So now we have found the smallest number in the array, which is -1
Swap the positions of -1 and 2 to complete the sorting of the first number
So now the array becomes
-1, 1, 2, 3, 0
Now the first number -1 is already in order, so it will not participate in the comparison and continue to the next
Now assume minval=1
2 is greater than 1, unchanged
3 is greater than 1, unchanged
0 is less than 1, then minval=0
Now that one cycle is completed, swap the positions of 0 and 1 to complete the sorting of the second number
So now the array becomes
-1, 0, 2, 3, 1
//The following push method is the same as above. . .
3. Insertion sort method description: First assume that the first number in an array is a separate ordered array, and then compare the following number with it [as I grows here, it becomes them]. If If the following number is smaller than the assumed number, move the smaller number back, and finally move that number to the front
The code is as follows | Copy code | ||||
$arr=array(2,1,- 1,3,0);
|
Understanding:
2, 1, -1, 3, 0
//For the first time, save the number 1 to be inserted as insertval, and then compare insertval with 2. 1 is less than 2, so move 2 back to become the following picture
2, 2, -1, 3, 0
//At this time, there is no number in front of 2, insertindex=0, so the comparison is completed, then insert insertval to the found position. It becomes as shown below
1, 2, -1, 3, 0
//At this time, 1 and 2 become ordered arrays
//The second time, first save the number to be inserted -1 as insertval, and then compare insertval with 2. -1 is less than 2, so move 2 back to become the following picture
1, 2, 2, 3, 0
//At this time, compare insertval with 1. If -1 is less than 1, then move -1 back to become the following picture (this is a process of comparing the number to be inserted with the previous ordered array)
1, 1, 2, 3, 0
//At this point, insertindex has come to an end, so insert insertval at this position
-1, 1, 2, 3, 0
//The following method is as above
The two-dimensional array sorting function can achieve an ORDER BY effect similar to MySQL. It has special applications when the array is not obtained from the database.
The code is as follows | Copy code |
// Description: Sorting method of two-dimensional array in PHP |
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php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($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。

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,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。


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