PHP file read and write operation learning

Note The!== operator does not exist before 4.0.0-RC2 if ($handle = Opendir ('/path/to/files ')) { echo "Directory handle: $handle \ n"; echo "files:\n"; while (false!== ($file = Readdir ($handle))) { echo "$file \ n"; } while ($file = Readdir ($handle)) { echo "$file \ n"; } Closedir ($handle); } ?> Copy Code Read the file: $file _name = "Data.dat"; Absolute path of the file to read: Homedata.dat $file _pointer = fopen ($file _name, "R"); Open file, 8. "R" is a pattern, 9. Or the way we're going to do it, 10. See the introduction later in this article $file _read = fread ($file _pointer, FileSize ($file _name)); By means of document 14. Pin Read File contents Fclose ($file _pointer); Close File Print "The contents of the file read: $file _read"; Show file contents ?> Copy Code Write file: $file _name = "Data.dat"; Absolute path: Homedata.dat $file _pointer = fopen ($file _name, "w"); "W" is a pattern, 8. See later Fwrite ($file _pointer, "What Do You Wanna Write"); Cut the file 12 first. is 0 bytes in size, 13. Then write Fclose ($file _pointer); End Print "Data successfully written to file"; ?> Copy Code Append to file after: $file _name = "Data.dat"; Absolute path: Homedata.dat $file _pointer = fopen ($file _name, "a"); "W" mode Fwrite ($file _pointer, "What Do You Wanna Append"); Not 11. Cut the file by 12. into 0 bytes, 13. Append data to the end of the file Fclose ($file _pointer); End Print "Data successfully appended to file"; ?> Copy Code The above is just a brief introduction, below we will discuss some deeper. Sometimes a multi-person write scenario (most often on a Web site with a large traffic) produces useless data written to the file, such as: Info.file file contents are as follows |1| mukul|15| male| India (n) |2| linus|31| male| Finland (N) Now two people registered 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 example above, when PHP writes Rob's information to a file, Bill also starts writing, which is exactly the time to write the ' n ' of the Rob record, causing file corruption. We certainly don't want this to happen, so let's take a look at the file lock: $file _name = "Data.dat"; $file _pointer = fopen ($file _name, "R"); $lock = Flock ($file _pointer, lock_sh); I use 4.0.2,9. So use lock_sh,10. You may need to write 1 directly. if ($lock) { $file _read = fread ($file _pointer, FileSize ($file _name)); $lock = Flock ($file _pointer, Lock_un); If the version is less than php4.0.2,17. Replace Lock_un with 3 } Fclose ($file _pointer); Print "File content is $file _read"; ?> Copy Code In the above example, if two files read.php and read2.php are to access the file, they can all be read, but when a program needs to write, it must wait until the read operation is complete and the file is freed. $file _name = "Data.dat"; $file _pointer = fopen ($file _name, "w"); $lock = Flock ($file _pointer, LOCK_EX); If the version is below php4.0.2,9. Replace LOCK_EX with 2 if ($lock) { Fwrite ($file _pointer, "What U Wanna Write"); Flock ($file _pointer, Lock_un); If the version is below php4.0.2,16. Replace Lock_un with 3 } Fclose ($file _pointer); Print "Data successfully written to file"; ?> Copy Code Although the "W" mode is used to overwrite the file, I don't think it applies. $file _name = "Data.dat"; $file _pointer = fopen ($file _name, "a"); $lock = Flock ($file _pointer, LOCK_EX); If the version is below php4.0.2,9. Replace LOCK_EX with 2 if ($lock) { Fseek ($file _pointer, 0, seek_end); If the version is less than php4.0rc1,15. Using Fseek ($file _pointer, filsize ($file _name)); Fwrite ($file _pointer, "What U Wanna Write"); Flock ($file _pointer, Lock_un); If the version is below php4.0.2,20. Replace Lock_un with 3 } Fclose ($file _pointer); Print "Data successfully written to file"; ?> Copy Code Hmmm., for append data is a little different from other operations, that is fseek! It is always a good practice to confirm that the file pointer is at the end. If it is under Windows system, the file name above must be preceded by a ". Flock: Flock () is locked only when the file is open. The file is locked after it is opened, and now the contents of the file are only in the content at that time and do not reflect the results of other program operations, so it is not only the file append operation, but also the read operation should use Fseek. (the translation may not be very precise here, but I think it's a good idea.) About the mode: ' R '-read-only open, the file pointer is placed in the file header ' r+ '-read and write mode open, the file pointer is placed in the file header ' W '-write-only open, the file pointer is placed in the file header, the file is cut to 0 bytes, if the file does not exist, try to establish the file The file size is cut to 0 bytes, if the file does not exist, try to establish the file ' a '-write-only open, the file pointer is placed at the end of the file, if the file does not exist, try to establish a file ' A + '-read and write open, the file pointer is placed at the end of the file, By the way, the code that creates the file directory Create a similar ". /.. /.. Directory of/xxx/xxx.txt " function Createdirs ($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 Create directory } } } Calls such as Createdirs ("xxx/xxxx/xxxx",); Use $globals["Dirseparator" in the original function I changed it to '/' function Recur_mkdirs ($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; } Copy Code The above article, for beginners Reference, master drift over.

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