PHP5 classic tutorial file operation_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 necessary in cms systems. 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 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 operations

The first introduction is a function that reads from a 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 directory information. 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 the free space.

Create command:

mkdir($path,0777)

, 0777 is the permission code, which can be set by the umask() function under non-window conditions.

rmdir($path)

The file with the path in $path will be deleted.

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 file handles, and then uses pointers. Read., see the php manual here:

$d = dir("/etc/php5");
echo "Handle: " . $d->handle . " ";
echo "Path: " . $d->path . " ";
while (false !== ($entry = $d->read())) {
    echo $entry." ";
}
$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.

3. File Operation

A. Read file

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(文件不存在或者无法读取);
} else {
         echo 存在;
}
?>

$file = dirlist.php;
if (is_readable($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 (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 (the 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 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));

B. Write file

Same as reading a file, first check if it can be written:

$file = dirlist.php;
if (is_writable($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");
}
?>

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