Directory operations and file operations in PHP_PHP tutorial

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 in cms systems are Necessary and very useful. We often encounter operations such as generating file directories and editing files (folders). 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 Consult 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 Operations

The first thing to introduce is a method of reading from a directory. The functions taken, opendir(), readdir(), closedir(), when used, first open the file handle, 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 about returning the file The files under the directory are already in the directory (0 files will return false).

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

Creation command:

mkdir($path,0777)

, 0777 is the permission code, in non- The umask() function can be set under 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. , there are 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:

$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

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

The attributes of the file are also very important. The 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 is a file To see if it 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('文件不存在或者无法读取');
} else {
         echo '存在';
}
?>

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('文件不存在');
}
$data = file_get_contents($file);
echo htmlentities($data);
?>

$file = " filelist.php";
if (file_exists($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, it 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 also a way to read binary files:

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

B. Writing files

is the same as reading files. First check if you can write:

$file = 'dirlist.php';
if (is_writable($file) == false) {
         die("我是鸡毛,我不能");
}
?>

$file = 'dirlist.php';
if (is_writable($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('我是鸡毛,我不能');
}
$data = '我是可鄙,我想要';
file_put_contents ($file, $data);
?>

The file_put_contents function is new in php5 The imported function (if you don’t know it exists, use the function_exists function to determine it first) cannot be used in lower versions of PHP. You can use the following method:

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

to replace it.

When writing a file, sometimes you need to lock it, and then write:

function cache_page($pageurl,$pagedata){
if(!$fso=fopen($pageurl,'w')){
$this->warns('无法打开缓存文件.');//trigger_error
return false;
}
if(!flock($fso,LOCK_EX)){//LOCK_NB,排它型锁定
$this->warns('无法锁定缓存文件.');//trigger_error
return false;
}
if(!fwrite($fso,$pagedata)){//写入字节流,serialize写入其他格式
$this->warns('无法写入缓存文件.');//trigger_error
return false;
}
flock($fso,LOCK_UN);//释放锁定
fclose($fso);
return true;
}

C. Copy and delete files

It is very easy to delete files in PHP. Use the unlink function to simply operate:

$file = 'dirlist.php';
$result = @unlink ($file);
if ($result == false) {
echo '蚊子赶走了';
} else {
echo '无法赶走';
}
?>

.

Copying files is also easy:

$file = 'yang.txt';
$newfile = 'ji.txt'; # 这个文件父文件夹必须能写
if (file_exists($file) == false) {
die ('小样没上线,无法复制');
}
$result = copy($file, $newfile);
if ($result == false) {
echo '复制记忆ok';
}
?>

$file = 'yang.txt';
$newfile = 'ji.txt'; # Parent folder of this file Must be able to write
if (file_exists($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.

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));
?>

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

Returns the unix timestamp, which is Caching technology is commonly used.

Relevant ones include obtaining the last access time fileatime(), filectime() when the file permissions, owner, all groups or other metadata in the inode are updated, fileowner () function returns the file owner

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

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

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

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

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

// 输出类似：somefile.txt: 1024 bytes

$filename = 'somefile.txt';
echo $filename . ': ' . filesize($filename) . ' bytes';

?>

filesize() returns File size in bytes:

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

// Output is similar: somefile.txt: 1024 bytes $filename = 'somefile.txt';
echo $filename . ': ' . filesize($filename) . ' bytes'; ?> Get All the information in the file has a function stat() function that returns an array:

You can check the detailed information about what the key corresponds to, which will not be expanded here.

http://www.bkjia.com/PHPjc/371506.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/371506.htmlTechArticleIn any computer device, files are necessary objects, and in web programming, file operations have always been It is a headache for web programmers, and file operations are necessary in the cms system...