PHP file operation example code_PHP tutorial-PHP Tutorial-php.cn

First send a simple example

Copy code The code is as follows:

 
if(!is_dir ('txt'))//Determine whether txt is a folder directory
{ 
mkdir('txt');//Create a folder directory named txt
$open=fopen('txt/ in.txt',"w+");//Open the file in read-write mode
if(is_writable('txt/in.txt'))//If this file is in writable mode
{ 
if(fwrite($open,"Today is a beautiful day, be happy! "- -"")>0)//Write content
fclose($open);//Close the file
echo "<script>alert('Write successfully');</script>";//Output success prompt
} 
} 
else 
{ 
if(is_file ('txt/in.txt'))//Determine whether the in.txt file exists in the directory
{ 
if(is_readable('txt/in.txt'))//Determine whether the file is readable
 { 
echo file_get_contents('txt/in.txt');//Output text information
unlink('txt/in.txt');//Delete file in.txt 
rmdir('txt' );//Delete directory 
} 
} 
} 
?> 

1. Introduction

In any computer device, files They are all necessary objects. In web programming, file operations have always been a headache for web programmers. However, file operations are necessary and very useful in cms systems. We often encounter generated files. Directory, file (folder) editing and other operations, now I will make a detailed summary of these functions in PHP and demonstrate how to use them with examples. For a detailed introduction to the corresponding functions, please refer to the PHP manual. Only the key points are summarized here. And what needs to be paid attention to (This is not available in the PHP manual.)

2. Directory operations

The first thing introduced is a function that reads from the directory, opendir(), readdir(), closedir (), when using it, open the file handle first, and then list it iteratively:

Copy the code The code is as follows:

 
< ;?php 
$base_dir = "filelist/"; 
$fso = opendir($base_dir); 
echo $base_dir."" ; 
while($flist= readdir($fso)){ 
echo $flist."
" ; 
} 
closedir($fso) 
?> 

This is a program that returns the files and directories under the file directory (0 files will return false).

Sometimes you need to know the directory information, you can use dirname($path) and basename($path), respectively Return the directory part and file name part of the path. You can use disk_free_space($path) to return the free space.

Creation command:

mkdir($path,0777)

,0777 is the permission code, which can be set by the umask() function under non-window conditions.

rmdir($path)

will delete the file with the path in $path.

The dir -- directory class is also an important class for operating file directories. It has three methods, read, rewind, and close. This is a pseudo-object-oriented class. It first uses a file handle to open the file, and then reads it using a pointer. ., see the php manual here:

Copy code The code is as follows:

 
$d = dir ("/etc/php5"); 
echo "Handle: " . $d->handle . "n"; 
echo "Path: " . $d->path . "n"; 
while (false !== ($entry = $d->read())) { 
echo $entry."n"; 
} 
$d->close(); 
?> 

Output:

Handle: Resource id #2
Path: /etc/php5
.
..
apache
cgi
cli

The attributes of the file are also very important. File attributes include creation time, last modification time, owner, file group, type, size, etc.

below Let’s focus on file operations.

3. File operations

● Reading files

First, check whether a file can be read (permission issue), or whether it exists No, we can use the is_readable function to get the information.:

Copy code The code is as follows:

 
 $file = 'dirlist.php'; 
if (is_readable($file) == false) { 
die('The file does not exist or cannot be read'); 
} else { 
echo 'Exists'; 
} 
?> 

The function to determine the existence of a file also includes file_exists (demonstrated below), but this is obviously not as comprehensive as is_readable. When a file exists, it can Use

to copy the code . The code is as follows:

 
$file = "filelist.php"; 
if (file_exists($file) == false) { 
die('File does not exist'); 
} 
$data = file_get_contents($file); 
echo htmlentities($data ); 
?> 

However, the file_get_contents function is not supported on lower versions. You can first create a handle to the file, and then use the pointer to read the entire file:

$fso = fopen($cacheFile, 'r');
$data = fread($fso, filesize($cacheFile));
fclose($fso);

There is another way to read binary files:

$ data = implode('', file($file));

● Writing a file

is the same as reading a file. First check if it can be written:

Copy code The code is as follows:

 

$file = 'dirlist.php'; 
if (is_writable($file) == false) { 
die("I am a chicken, I can't"); 
} 
?> 

If you can write, you can Use the file_put_contents function to write:

Copy code The code is as follows:

 
$file = 'dirlist .php'; 
if (is_writable($file) == false) { 
die('I am a chicken feather, I can't'); 
} 
$data = 'I am despicable, I Want'; 
file_put_contents ($file, $data); 
?> 

file_put_contents function is a newly introduced function in php5 (if you don’t know it exists, use the function_exists function to determine it first) (a) Low version of PHP cannot be used, you can use the following method:

Copy code The code is as follows:

 
$f = fopen ($file, 'w'); 
fwrite($f, $data); 
fclose($f); 

Replace it.

Write file Sometimes you need to lock, and then write:

Copy code The code is as follows:

 
function cache_page($pageurl,$pagedata ){ 
if(!$fso=fopen($pageurl,'w')){ 
$this->warns('Unable to open cached file.');//trigger_error 
return false; 
} 
if(!flock($fso,LOCK_EX)){//LOCK_NB, exclusive lock
$this->warns('Unable to lock cache file.');//trigger_error 
return false; 
} 
if(!fwrite($fso,$pagedata)){//Write byte stream, serialize writes other formats
$this->warns('Unable Write to cache file.');//trigger_error 
return false; 
} 
flock($fso,LOCK_UN);//Release lock
fclose($fso); 
return true ; 
} 

● Copy and delete files

It is very easy to delete files in php. It is a simple operation with the unlink function:

Copy Code The code is as follows:

 
$file = 'dirlist.php'; 
$result = @unlink ($file); 
if ($result == false) { 
echo 'The mosquitoes were driven away'; 
} else { 
echo 'Can't be driven away'; 
} 
?> 
 

That’s it.

Copying files is also easy:

Copy code The code is as follows:

 
$file = 'yang.txt'; 
$newfile = 'ji.txt'; # The parent folder of this file must be writable
if (file_exists($file) == false) { 
die ('The demo is not online and cannot be copied'); 
} 
$result = copy($file, $newfile); 
if ($result == false) { 
echo 'Copy memory ok'; 
} 
?> 

You can use the rename() function to rename a folder. Other operations are these functions It can be achieved by combining it.

● Get file attributes

Let me talk about a few common functions:
Get the latest modification time:

Copy code The code is as follows:

 
$file = 'test.txt'; 
echo date('r', filemtime($ file)); 
?> 

The returned timestamp is the unix timestamp, which is commonly used in caching technology.

is also related to getting the last access time fileatime(), filectime() When the file's permissions, owner, all groups or other metadata in the inode are updated, the fileowner() function returns the file owner

$owner = posix_getpwuid(fileowner($ file));

(non-window system), ileperms() obtains the permissions of the file,

Copy code The code is as follows:

 
$file = 'dirlist.php'; 
$perms = substr(sprintf('%o', fileperms($file)), -4); 
echo $perms; 
?> 

filesize() returns the file size in bytes:

Copy codeThe code is as follows:

 
// Output is similar: somefile.txt: 1024 bytes 
$filename = 'somefile.txt'; 
echo $filename . ': ' . filesize($ filename) . ' bytes'; 
?> 

To get all the information of the file, there is a function stat() function that returns an array:

Copy the code The code is as follows:

 
$file = 'dirlist.php'; 
$perms = stat($file); 
var_dump($perms); 
?> 

You can check the detailed information about which key corresponds, and will not expand it here.

4. Conclusion

I briefly summarized several file operations above. If you are proficient in the functions listed above, there will be no major problems in the operation. The functions of PHP file operations change relatively quickly and are now very powerful. File This part is also a very important part of learning PHP, I hope you won’t ignore it.