Detailed discussion of directory and file operations—PHP

Detailed discussion of directory and file operations—PHP_PHP tutorial

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Release： 2016-07-21 16:00:43

Original

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Reprinted from blueidea.com

1. Introduction
In any computer device, files are necessary objects, and in web programming, file operations have always been web programs However, file operations are necessary and very useful in the CMS system. We often encounter operations such as generating file directories and editing files (folders). Now I will make these functions in PHP Detailed summary and examples to demonstrate how to use. For a detailed introduction to the corresponding functions, please refer to the PHP manual. Here we only summarize the key points and what needs attention. (This is not found in the PHP manual.)

2. Directory operation
The first introduction is a function that reads from the directory, opendir(), readdir(), closedir(). When used, the file handle is opened first, and then iteratively listed:
$base_dir = "filelist/";
$fso = opendir($base_dir);
echo $base_dir."

" ;
while ($flist=readdir($fso)){
echo $flist."
" ;
}
closedir($fso);
?>
This It 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) to return respectively For the directory part and file name part of the path, disk_free_space($path) can be used to return the free space.

Creation command:
mkdir($path,0777)
, 0777 is the permission code, It can be set with the umask() function under non-window conditions.

rmdir($path)
will delete files with paths in $path.

dir -- the directory class also operates file directories. 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
The attributes of the file 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, see if a file can be read (Permission issue), or if it exists, we can use the is_readable function to obtain the information.:
$file = 'dirlist.php';
if (is_readable($file) == false ) {
die('The file does not exist or cannot be read');
} else {
echo 'Exists';
}
?>
Function to determine the existence of a file There is also 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);
?> ;
However, the file_get_contents function is not supported in lower versions. You can first create a handle to the file, and then use the pointer to read all:
$fso = fopen($cacheFile, 'r');
$ data = fread($fso, filesize($cacheFile));
fclose($fso);
There is another way to read binary files:
$data = implode('', file ($file));

Writing a file

The same way as reading a file, first check if it can be written:

$file = 'dirlist.php';
if (is_writable($file) == false) {
die("I am a chicken feather, I can't");
}
?> ;
If you can write, you can use the file_put_contents function to write:
$file = 'dirlist.php';
if (is_writable($file) == false) {
die('I am a chicken feather, I can't');
}
$data = 'I am despicable, I want';
file_put_contents ($file, $data);
? >
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:
function cache_page($pageurl,$pagedata){
if(!$fso=fopen($pageurl,'w')){
$this->warns('Unable to open cache file.') ;//trigger_error
return false;
}
if(!flock($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 to write other formats
$this->warns('Unable to write cache file.');/ /trigger_error
return false;
}
flock($fso,LOCK_UN);//Release lock
fclose($fso);
return true;
}

Copy and delete files

It is very easy to delete files in php. It is simple to use the unlink function:
$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:
$file = 'yang.txt';
$newfile = 'ji.txt'; # The parent folder of this file must be writable
if (file_exists($file) == false) {
die ('The sample 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 can be achieved by combining these functions.

Get file attributes

I will talk about a few common ones Function:
Get the latest modification time:
$file = 'test.txt';
echo date('r', filemtime($file));
?>
The returned timestamp is the Unix timestamp, which is commonly used in caching technology.

Related are also the fileatime(), filectime(), file permissions for the last accessed time, all Or, the time when metadata in all groups or other inodes is updated, the fileowner() function returns the file owner
$owner = posix_getpwuid(fileowner($file));
(non-window system), ileperms() Get file permissions,
$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';
?>
There is a return array for getting all the information of the file Function stat() function:
$file = 'dirlist.php';
$perms = stat($file);
var_dump($perms);
? >
You can check the detailed information about what the key corresponds to, which will not be expanded here.

4. Conclusion

I briefly summarized a few of them above File operation, if you are proficient in the functions listed above, there will be no big problems when operating. The functions of PHP file operation change quickly and are now very powerful. The file part is also a very important part of learning PHP. I hope Don't ignore it.