(Advanced) Commonly used file operation functions in PHP

The following are PHP file operation functions. Of course, this is just part of it, there are many more that I didn’t list.

1. Parse the path:

1 Get the file name:

basename();
Gives a string containing the full path to a file, This function returns the base file name. If the filename ends with suffix, this part will also be removed.
eg:

$path = "/home/httpd/html/index.php";
$file = basename($path,".php"); // $file is set to "index"

2 Get the directory part:
dirname();
Gives a string containing the full path to a file , this function returns the directory name after removing the file name.
eg:

$path = "/etc/passwd";
$file = dirname($path); // $file is set to "/etc"

3 Get the path associative array
pathinfo();
Get the three parts of a specified path: directory name, basic Name, extension.
eg:

$pathinfo = pathinfo("www/test/index.html");
var_dump($pathinfo);
// $path['dirname']
$path['basename']
$path['extenssion']

2. File type
1. filetype();
Returns the type of file. Possible values ​​are fifo, char, dir, block, link, file and unknown.
eg:

echo filetype('/etc/passwd'); // file
echo filetype('/etc/');        // dir

3. Get an array of useful information for a given file (very useful)

1. fstat();
Through the opened The file pointer obtains file information
Obtains the statistical information of the file opened by the file pointer handle. This function is similar to the stat() function, except that it operates on an open file pointer instead of a file name.
eg:

// 打开文件
$fp = fopen("/etc/passwd", "r");
// 取得统计信息
$fstat = fstat($fp);
// 关闭文件
fclose($fp);
// 只显示关联数组部分
print_r(array_slice($fstat, 13));

2. stat()
Get the statistical information of the file specified by filename (analogous to fstat())

4. Calculate the size
1. filesize()
Returns the number of bytes of the file size. If an error occurs, it returns FALSE and generates an E_WARNING level error.
eg:

// 输出类似：somefile.txt: 1024 bytes
$filename = 'somefile.txt';
echo $filename . ': ' . filesize($filename) . ' bytes';

2. disk_free_space()
Get the available space (in bytes) of the disk partition where the directory is located
eg

// $df 包含根目录下可用的字节数
$df = disk_free_space("/");
//在 Windows 下:
disk_free_space("C:");
disk_free_space("D:");

3. disk_total_space()
Returns the total disk size of a directory
eg: (same as above, replace the function)

Another: If you need to calculate the size of a directory, you can write A recursive function to implement

Code

function dir_size($dir){
$dir_size = 0;
if($dh = @opendir($dir)){
while(($filename = readdir($dh)) != false){
if($filename !='.' and $filename !='..'){
     if(is_file($dir.'/'.$filename)){
$dir_size +=filesize($dir.'/'.$filename);
}else if(is_dir($dir.'/'.$filename)){
      $dir_size +=dir_size($dir.'/'.$filename);
}
}
                   }#end while
            }# end opendir
@closedir($dh);
return $dir_size;
} #end function

5. Access and modification time
1. fileatime(): Last access time
2 . filectime(): Last change time (modification of any data)
3. filemtime(): Last modification time (referring to content modification only)

6. File I /O operation

1. fopen -- Open a file or URL

mode Description
'r' Open in read-only mode and point the file pointer to the file header.
'r+' Open in read-write mode and point the file pointer to the file header.
'w' turns on writing mode, points the file pointer to the file header and truncates the file size to zero. If the file does not exist, try to create it.
'w+' Open in read-write mode, point the file pointer to the file header and truncate the file size to zero. If the file does not exist, try to create it.
'a' opens in writing mode and points the file pointer to the end of the file. If the file does not exist, try to create it.
'a+' Open in read-write mode and point the file pointer to the end of the file. If the file does not exist, try to create it.
'x' creates and opens for writing, pointing the file pointer to the file header. If the file already exists, the fopen() call fails and returns FALSE,
'x+' is created and opened for reading and writing, pointing the file pointer to the file header. If the file already exists, the fopen() call fails and returns FALSE
eg:

$handle = fopen("/home/rasmus/file.txt", "r");

2. file -- Read the entire file into an array (this function is very useful)
Same as file_get_contents(), except that file() treats the file as an Array returned. Each cell in the array is a corresponding line in the file, including newlines. If file() fails, it returns FALSE.
eg:

Code

$lines = file('http://www.example.com/');
// 在数组中循环，显示 HTML 的源文件并加上行号。
foreach ($lines as $line_num => $line) {
echo "Line #<b>{$line_num}</b> : " . htmlspecialchars($line) . "<br />\n";
}
// 另一个例子将 web 页面读入字符串。参见 file_get_contents()。
$html = implode(&#39;&#39;, file (&#39;http://www.example.com/&#39;));

3. fgets -- Read a line from the file pointer
Pointed to by handle Reads a line from the file and returns a string with a length of at most length - 1 bytes. Stops when a newline character (included in the return value), EOF, or length - 1 bytes has been read (whichever occurs first). If length is not specified, it defaults to 1K, or 1024 bytes.
eg:

$handle = @fopen("/tmp/inputfile.txt", "r");
if ($handle) {
while (!feof($handle)) {
$buffer = fgets($handle, 4096);
echo $buffer;
}
fclose($handle);
}

4. fgetss -- Read a line from the file pointer and filter out HTML tags
Same as fgets(), except fgetss Try stripping any HTML and PHP markup from the text you read.

You can use the optional third parameter to specify which tags will not be removed

Another: Operations on the directory:
1. opendir -- open the directory handle, Opens a directory handle that can be used in subsequent closedir(), readdir(), and rewinddir() calls.
2. readdir -- Read the entry from the directory handle and return the file name of the next file in the directory. File names are returned in order in the file system.
eg:

Code

// 注意在 4.0.0-RC2 之前不存在 !== 运算符
if ($handle = opendir('/path/to/files')) {
echo "Directory handle: $handle\n";
echo "Files:\n";
  
while (false !== ($file = readdir($handle))) {
echo "$file\n";
}
   
while ($file = readdir($handle)) {
echo "$file\n";
}
     closedir($handle);
}

3. scandir -- List the files and directories in the specified path (very Useful), returns an array containing the files and directories in directory.
The default sort order is in ascending alphabetical order. If the optional parameter sorting_order is used (set to 1), the sort order is descending alphabetical order.
eg:

$dir    = '/tmp';
$files1 = scandir($dir);
$files2 = scandir($dir, 1);
print_r($files1);
print_r($files2);

另外注：

七、 对文件属性的操作（操作系统环境不同，可能有所不一样，这点要注意）

1文件是否可读：

       boolis_readable ( string filename )

如果由 filename 指定的文件或目录存在并且可读则返回 TRUE。

记住 PHP 也许只能以运行 webserver 的用户名（通常为 'nobody'）来访问文件。不计入安全模式的限制。

2 文件是否可写

         bool is_writable ( string filename )

如果文件存在并且可写则返回 TRUE。filename 参数可以是一个允许进行是否可写检查的目录名。

记住 PHP 也许只能以运行 webserver 的用户名（通常为 'nobody'）来访问文件。不计入安全模式的限制

3 检查文件是否存在

    boolfile_exists ( string filename )

      如果由 filename 指定的文件或目录存在则返回 TRUE，否则返回 FALSE

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