PHP5 Tutorial File Operation_PHP Tutorial

1. Introduction

In any computer device, files are necessary objects, and in web programming, the operation of files has always been a headache for web programmers, and , file operations are necessary and very useful in the CMS system. We often encounter operations such as generating file directories, editing files (folders), etc. Now I will give 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. Here we only summarize the key points and points that need attention. (This is not available in the PHP manual.) (www.bkjia.com)

II , 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:

$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 returns 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 path in $ The file of path.

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 open files. The handle is then read 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 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

A. 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('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

$file = "filelist.php";
if (file_exists($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 a pointer to read all of it:

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

There is another way to read binary File:

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

B. Writing files

is the same as reading files , first see if you can write:

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

The file_put_contents function is newly introduced in php5 function (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);

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
$this->warns('Unable Lock the cache file.');//trigger_error
return false;
}
if(!fwrite($fso,$pagedata)){//Write byte stream, serialize writes other formats
$this->warns('Unable to write to cache file.');//trigger_error
return false;
}
flock($fso,LOCK_UN);//Release lock
fclose($fso);
return true;
}

C. Copy and delete files

It is very easy to delete files in php, use the unlink function: 🎜>

$file = 'dirlist.php';
$result = @unlink ($file);
if ($result == false) {
echo 'Mosquitoes are driven away';
} else {
echo 'Cannot 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 file Clip. Other operations can be achieved by combining these functions.

D. Get file attributes

I will talk about a few common functions:

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.

Relevantly, fileatime() and filectime() are used to obtain the last accessed time and file permissions. The time when the owner, 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() obtains file permissions,

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

filesize() returns the file size in bytes Number:

// 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:

$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 several file operations above. You are proficient in the functions listed above, and there are no major problems when operating them. 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

http://www.bkjia.com/PHPjc/371497.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/371497.htmlTechArticle1. Introduction In any computer device, files are necessary objects, and in web programming, File operations have always been a headache for web programmers, and file operations in the cms system...