File operations in php

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File operation
Commonly used functions
file()
Read each line in the file into an array
parse_ini_file()
Used to parse a configuration file
Note: If the second parameter is set to true, you will get A multidimensional array. Includes the name and settings of each category (section) in the configuration file
file_get_contents()
Read the entire file into a string
file_put_contents()
Write the string to the file. If the file does not exist, it will be created automatically
\r and \n are The difference
\rEnter
Tell the typewriter to position the print head to the left
\nLine feed
Tell the typewriter to move the paper down one line
Differences between systems
In Linux system\n
windows Inside, line breaks are using \r\n
In the mac system, each line is \r
Opening and closing of files
Open a file and obtain resources
fopen('location of file','mode')
Return the resources of a file
Mode
r
Open in read-only mode, the file pointer points to the head of the file, and an error will be reported if the file does not exist
r
Open in reading and writing mode. The file pointer starts from the head and covers the written part. If the file does not exist, an error will be reported.
w
Opening in writing mode , point the file pointer to the head of the file and truncate the file size to 0
w
Open in read-write mode, point the file pointer to the head of the file and truncate the file The size is truncated to 0
a
Open in writing mode, point the file to the end of the file (write to the file in append mode), and create the file if it does not exist
a
Open in read-write mode, point the file to the end of the file, create it if it does not exist, and start from the beginning when reading
The difference between w and r is whether to create the file if it does not exist
Experience
Least privilege principle
Operation file
fgets (resource)
Read one line at a time, and move the pointer down when reading one line
fgetc (resource)
Read one byte at a time, moving the pointer downward
fread (resource, number of characters)
Read the specified number of characters
feof (resource)
Return true when there is a file error or the pointer has pointed to the end of the file
fwrite (resource, write content)
Write the content to the file pointer
Close the resource
fclose(resource)
Note
Resources are opened and closed. Even if these resources are closed without using code, they will be automatically released after all the code is executed.
File locking mechanism
flock (resource, option)
Option
LOCK_SH, when reading the file, others should not write content in it
LOCK_EX, when writing a file, others cannot read or write the file
LOCK_UN, release the lock
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