


After reading this article about the difference between file_exists and is_file, is_dir in PHP, I basically understand that PHP's file_exists = is_dir + is_file.
Write a program to verify:
Execute 1000 times each and record the time required.
File exists (current directory)
is_file:0.4570ms
file_exists:2.0640ms
File exists (absolute path level 3/www/hx/a/)
is_file:0.4909ms
file_exists:3.3500ms
File exists (absolute path level 5/www/hx/a/b/c/)
is_file:0.4961ms
file_exists:4.2100ms
The file does not exist (current directory)
is_file:2.0170ms
file_exists:1.9848ms
The file does not exist (absolute path level 5/www/hx/a/b/ c/)
is_file:4.1909ms
file_exists:4.1502ms
Directory exists
file_exists:2.9271ms
is_dir:0.4601ms
Directory does not exist
file_exists: 2.9719ms
is_dir:2.9359ms
is_file($file)
file_exists($file)
When $file is a directory, is_file returns false and file_exists returns true
When the file exists, is_file is much faster than file_exists;
The deeper the directory where the file is to be detected, the greater the speed difference, but it is at least 4 times faster.
When the file does not exist, is_file is a little slower than file_exists, but it can be ignored.
When the directory exists, is_dir is much faster than file_exists;
When the directory does not exist, is_dir is a little slower than file_exists, but it can be ignored.
Conclusion:
If you want to determine whether the file exists, use the function is_file(),
If you want to determine whether the directory exists, use the function is_dir(),
There seems to be no place to use file_exists. Is it used when you are not sure whether the parameter passed in is a file or a directory?

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。

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。

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。

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。


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Dreamweaver Mac version
Visual web development tools

Atom editor mac version download
The most popular open source editor

WebStorm Mac version
Useful JavaScript development tools

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

Notepad++7.3.1
Easy-to-use and free code editor
