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Detailed discussion of directory and file operations in php_PHP tutorial
Detailed discussion of directory and file operations in php_PHP tutorial
1. Introduction
In any computer device, files are necessary objects. In web programming, file operations have always been a headache for web programmers. However, file operations are very difficult in cms systems. It is necessary and very useful. We often encounter operations such as generating file directories, editing files (folders), etc. Now I will make a detailed summary of these functions in PHP and demonstrate how to use them with examples. Regarding the corresponding functions in detail, Please refer to the PHP manual. Here we only summarize the key points and points that need attention. (This is not found in the PHP manual.)
2. Directory operation
The first one introduced is a function that reads from the directory, opendir (), readdir(), closedir(), when used, open the file handle first, and then list it iteratively:
$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.
dir -- directory class also operates the file directory. The important class has three methods, read, rewind, and close. This is a pseudo-object-oriented class. It first uses a file handle to open and then reads it using a pointer. See the PHP manual here:
$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
file The attributes are also very important. File attributes include creation time, last modification time, owner, file group, type, size, etc.
Let’s focus on file operations below.
3. File operations
● Reading files
First, check whether a file can be read (permission issue), or whether it exists. We can use the is_readable function to obtain the information.:
$file = 'dirlist.php';
if (is_readable($file) == false) {
die('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, you can use
$file = "filelist.php";
if (file_exists($file) == false) {
die('File does not exist');
}
$data = file_get_contents($file);
echo htmlentities($data);
?>
But the file_get_contents function is not supported on lower versions, you can create it first 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));
● Write file
and read The file method is the same, first check if it can be written:
$file = 'dirlist.php';
if (is_writable($file) == false) {
die("I am a chicken, I can't" ; As follows:
$file = 'dirlist.php';
if (is_writable($file) == false) {
The 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). Lower versions of PHP cannot be used. You can use the following method:
$f = fopen($file, 'w ');
fwrite($f, $data);
fclose($f);
Replace it.
Sometimes you need to lock when writing a file, then write:
The code is as follows:
function cache_page($pageurl,$pagedata){
if(!$fso=fopen($pageurl ,'w')){
$this->warns('Unable to open cache file.');//trigger_error
$this->warns('Unable to write cache file.');//trigger_error
return false;
}
flock($fso,LOCK_UN);//Release the lock
fclose($fso);
return true;
}
● Copy and delete files
It is very easy to delete files in php. It is simple to use the unlink function:
Copy code
The code is as follows:
$file = 'dirlist.php';
$result = @unlink ($file);
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
?>
You can use the rename() function to rename a folder. Other operations can be achieved by combining these functions.
● Get file attributes
Let me tell you a few Common functions:
Get the latest modification time:
Copy code
The code is as follows:
$file = 'test.txt';
echo date('r', filemtime($file));
(non-window system), ileperms() obtains the file permissions,
Copy code
The code is as follows:
$file = 'dirlist.php';
$perms = substr(sprintf('%o', fileperms($file)), -4);
echo $perms;
?>
filesize() returns the number of bytes of the file size:
// The output is similar: somefile.txt: 1024 bytes
$filename = 'somefile.txt';
echo $filename . ': ' . filesize($filename) . ' bytes';
?>
$file = 'dirlist.php';
$perms = stat($file ; I briefly summarized several file operations above. If you are proficient in the functions listed above, there will be no big problems when operating. The functions of PHP file operations change relatively quickly and are now very powerful. The file part It is also a very important part of learning php, I hope you will not ignore it.
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