File reading, writing, and deletion operations in PHP (file and directory operations in PHP)_PHP tutorial

1: Directory operation
The first thing introduced is a function that reads from the directory, opendir(), readdir(), closedir(). When used, the file handle is opened first, and then iteratively listed :

Copy code The code is as follows:

　　$base_dir = "filelist/";
$fso = opendir($base_dir);
echo $base_dir."

---

" ;
while($flist=readdir($fso)){
echo $flist."< ;br/>" ;
　}
　closedir($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 information of the directory. You can use dirname($path) and basename($path) to return the directory part and file name part of the path respectively. You can use disk_free_space($path) to return it. Space free space.
　Creation command:
　mkdir($path,0777)
　,0777 is the permission code, which can be set by the umask() function under non-window.
　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, 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();
　?>
[code]
　Output:
　Handle: Resource id #2
　Path: /etc/php5
. , type, size, etc.
Now let’s focus on file operations.

Two: File operations

Reading files
The first is to see if a file can be read (permission issue), Or if it exists, we can use the is_readable function to obtain the information.:
[code] 　　$file = 'dirlist.php';
　if (is_readable($file) == false) {
die('The file does not exist or cannot be read');
} else {
echo 'exists';
}
?>


There is also file_exists (demoed below) to determine the existence of a file, but this is obviously not as comprehensive as is_readable. When a file exists, you 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);
　?>


But the file_get_contents function is It 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:

Copy the code

The code is as follows:

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

There is another way to read binary files:
$data = implode('', file($file));

Learn in detail how to operate files and directories in PHP

1: Introduction
In any computer device, files are necessary objects, and in web programming, file operations have always been a headache for web programmers. 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 a detailed summary and examples of these functions in PHP. 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 points that need attention. (This is not found in the PHP manual.)
2: Directory Operation The first thing introduced is a function that reads from a directory, opendir(), readdir(), closedir(). When used, the file handle is opened first, and then iteratively listed:


Copy code
The code is as follows:

$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 , it can be set with the umask() function under non-window conditions.
rmdir($path) will delete the file with the path in $path.
dir -- directory class is also an important class for operating file directories. It has 3 methods, read, rewind, 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:

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 Including creation time, last modification time, owner, file group, type, size, etc.
Let’s focus on file operations below.
Three: File operations
Read files
First It is a file to see if it can be read (permission issue), or whether it exists. We can use the is_readable function to obtain 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 (demoed below) , but this is obviously not as comprehensive as is_readable. When a file exists, you 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 create a handle to the file first. , 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));
Write file
and read The way to get the file is the same, first see if you can write:

Copy the code The code is as follows:

$file = 'dirlist.php';
if (is_writable($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:

Copy the code The code is as follows:

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

file_put_contents function in The newly introduced functions in php5 (if you don’t know if they exist, use the function_exists function to check first) are not available in lower versions of php. 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:

Copy the code The code is as follows:

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 writes other formats
$this->warns('Unable to write cache file.');//trigger_error
return false;
}
flock($fso,LOCK_UN);//Release lock
fclose($fso);
return true;
}

Copy, delete files
php Deleting files is very easy. Use the unlink function to operate simply:

Copy the 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.
Copy Files are 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, it cannot be copy');
}
$result = copy($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
Let me talk about a few common functions:
Get the latest modification time:

Copy the code The code is as follows:

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

The returned one is unix Timestamp, which is commonly used in caching technology.
Relevant are also getting the time when the file was last accessed fileatime(), filectime() when the file's permissions, owner, all groups or other metadata in the inode are updated Time, the fileowner() function returns the file owner $owner = posix_getpwuid(fileowner($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 file size in bytes:

Copy code The code is as follows:

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

Get all the information of the file and there is a return array The function stat() function:

Copy code The code is as follows:

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

You can check the detailed information for what the key corresponds to. It will not be expanded here.
Four: Conclusion
I briefly summarized several file operations above. If you are proficient in the functions listed above, it is not a big deal when you are already operating. The problem is that the functions of PHP file operations change quickly and are now very powerful. The file part is also a very important part of learning PHP. I hope you will not ignore it.

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