File reading and writing operations in PHP_PHP tutorial-PHP Tutorial-php.cn

File reading and writing operations in PHP

PHP provides a series of I/O functions that can easily implement the functions we need, including file system operations and directory operations (such as "copy"). The following introduces you to the basic file reading and writing operations: (1) reading files; (2) writing files; (3) appending to files.

The following is an article about basic file reading and writing operations. I once learned the basic file operations after reading this article. I post it here to share with everyone:
Read file:
PHP code:
1. 2.
3. $file_name = "data.dat";
4. // Absolute path of the file to be read: homedata.dat
5.
6. $file_pointer = fopen($file_name, "r");
7. // Open the file, 8. "r" is a mode, 9. Or the operation method we want to perform, 10. See the introduction later in this article for details
11.
12. $file_read = fread($file_pointer, filesize($file_name));
13. // Read the file content through the file pointer 14.
15.
16. fclose($file_pointer);
17. //Close file
18.
19. Print "The content of the file read is: $file_read";
20. // Display file content
21. ?>
22.

Write file:
PHP code:
1. 2.
3. $file_name = "data.dat";
4. // Absolute path: homedata.dat
5.
6. $file_pointer = fopen($file_name, "w");
7. // "w" is a mode, 8. See below for details
9.
10. fwrite($file_pointer, "what you wanna write");
11. // First cut the file 12. to 0 bytes, 13. Then write
14.
15. fclose($file_pointer);
16. // End
17.
18. print "Data written to file successfully";
19.
20. ?>
21.

Append to the end of the file:
PHP code:
1. 2.
3. $file_name = "data.dat";
4. // Absolute path: homedata.dat
5.
6. $file_pointer = fopen($file_name, "a");
7. // "w" mode
8.
9. fwrite($file_pointer, "what you wanna append");
10. // No 11. Cut the file 12. into 0 bytes, 13. Append the data to the end of the file
14.
15. fclose($file_pointer);
16. // End
17.
18. print "Data successfully appended to file";
19.
20. ?>
21.

The above is just a brief introduction, below we will discuss some deeper ones.

Sometimes multiple people write (most commonly on websites with large traffic), which results in useless data being written to the file, for example:

The content of the info.file file is as follows ->

|1|Mukul|15|Male|India (n)
|2|Linus|31|Male|Finland (n)

Now two people register at the same time, causing file damage->

info.file ->

|1|Mukul|15|Male|India
|2|Linus|31|Male|Finland
|3|Rob|27|Male|USA|
Bill|29|Male|USA

In the above example, when PHP writes Rob's information to the file, Bill also starts writing. At this time, it happens that the 'n' recorded by Rob needs to be written, causing the file to be damaged.

We certainly don’t want this to happen, so let’s look at file locking:
PHP code:
1. 2.
3. $file_name = "data.dat";
4.
5. $file_pointer = fopen($file_name, "r");
6.
7. $lock = flock($file_pointer, LOCK_SH);
8. // I use 4.0.2, 9. So use LOCK_SH, 10. You may need to write it directly as 1.
11.
12. if ($lock) {
13.
14. $file_read = fread($file_pointer, filesize($file_name));
15. $lock = flock($file_pointer, LOCK_UN);
16. // If the version is less than PHP4.0.2, 17. Use 3 instead of LOCK_UN
18.
19. }
20.
21. fclose($file_pointer);
22.
23. Print "The file content is $file_read";
24.
25. ?>
26.

In the above example, if both files read.php and read2.php have to access the file, then they can both read it, but when a program needs to write, it must wait until the read operation is completed and the file is release.
PHP code:
1. 2.
3. $file_name = "data.dat";
4.
5. $file_pointer = fopen($file_name, "w");
6.
7. $lock = flock($file_pointer, LOCK_EX);
8. // If the version is lower than PHP4.0.2, 9. Use 2 instead of LOCK_EX
10.
11. if ($lock) {
12.
13. fwrite($file_pointer, "what u wanna write");
14. flock($file_pointer, LOCK_UN);
15. // If the version is lower than PHP4.0.2, 16. Use 3 instead of LOCK_UN
17.
18. }
19.
20. fclose($file_pointer);
21.
22. print "Data written to file successfully";
23.
24. ?>
25.

Although "w" mode is used to overwrite files, I don't think it is applicable.
PHP code:
1. 2.
3. $file_name = "data.dat";
4.
5. $file_pointer = fopen($file_name, "a");
6.
7. $lock = flock($file_pointer, LOCK_EX);
8. // If the version is lower than PHP4.0.2, 9. Use 2 instead of LOCK_EX
10.
11. if ($lock) {
12.
13. fseek($file_pointer, 0, SEEK_END);
14. // If the version is smaller than PHP4.0RC1, 15. Use fseek($file_pointer, filsize($file_name));
16.
17. fwrite($file_pointer, "what u wanna write");
18. flock($file_pointer, LOCK_UN);
19. // If the version is lower than PHP4.0.2, 20. Use 3 instead of LOCK_UN
21.
22. }
23.
24. fclose($file_pointer);
25.
26. print "Data written to file successfully";
27.
28. ?>
29.

Hmmm..., appending data is a little different from other operations, it's FSEEK! It's always a good habit to make sure the file pointer is at the end of the file.

If it is under Windows system, the file name in the above file needs to be preceded by ''.

FLOCK Talk:

Flock() only locks the file after it is opened. In the above column, the file is locked after it is opened. Now the content of the file is only the content at that time, and does not reflect the results of other program operations. Therefore, fseek should be used not only for file append operations, but also for read operations.
(The translation here may not be exact, but I think I get the idea).

About the pattern:

'r' - Open in read-only mode, the file pointer is placed at the file header

'r+' - Open in read-write mode, the file pointer is placed at the file header

'w' - Open for writing only, the file pointer is placed at the beginning of the file, the file is cut to 0 bytes, if the file does not exist, try to create the file

'w+' - Open for reading and writing, the file pointer is placed at the file header, the file size is cut to 0 bytes, if the file does not exist, try to create the file

'a' - Open for writing only, the file pointer is placed at the end of the file, if the file does not exist, try to create the file

'a+' - Open for reading and writing, the file pointer is placed at the end of the file, if the file does not exist, try to create the file

By the way, the code to create the file directory

//Create a directory similar to "../../../xxx/xxx.txt"

function createdirs($path, $mode = 0777) //mode 077
{
$dirs = explode('/',$path);
$pos = strrpos($path, ".");
if ($pos === false) { // note: three equal signs
// not found, means path ends in a dir not file
$subamount=0;
}
else {
$subamount=1;
}

for ($c=0;$c < count($dirs) - $subamount; $c++) {
$thispath="";
for ($cc=0; $cc <= $c; $cc++) {
$thispath.=$dirs[$cc].'/';
}
if (!file_exists($thispath)) {
//print "$thispath
";
mkdir($thispath,$mode); //mkdir function creates directory
}
}
}
//Call like createdirs("xxx/xxxx/xxxx",);

//The original function used $GLOBALS["dirseparator"] and I changed it to '/'

function recur_mkdirs($path, $mode = 0777) //mode 0777
{
//$GLOBALS["dirseparator"]
$dirs = explode($GLOBALS["dirseparator"],$path);
$pos = strrpos($path, ".");
if ($pos === false) { // note: three equal signs
// not found, means path ends in a dir not file
$subamount=0;
}
else {
$subamount=1;
}

These are just some basic file operation codes. I believe they are very useful for beginners. I post them here, hoping to inspire others!