Eight common file operations in PHP applications-PHP Tutorial

Eight common file operations in PHP applications. The unique PHP syntax is a mix of C, Java, Perl, and PHP self-innovative syntaxes. PHP can execute dynamic web pages faster than CGI or Perl. Dynamic pages made using PHP are a mix of C, Java, Perl, and PHP self-innovative syntaxes with the unique syntax of PHP. PHP can execute dynamic web pages faster than CGI or Perl. Compared with other programming languages, PHP embeds programs into HTML documents for execution. the execution efficiency is much higher than the CGI that generates HTML tags completely; PHP can also execute the compiled code, which can encrypt and optimize code execution to make code run faster. PHP has very powerful functions, all CGI functions can be implemented by PHP, and supports almost all popular databases and operating systems.

File and directory operations

PHP is very convenient to process files and directories on the local server, but sometimes the permission and path problems may occur.

1. open the file

Resource fopen (string filename, string mode [, bool use_include_path [, resource zcontext])

$ Handle = fopen (filename, mode) // open the file and return a handle representing the resource of the file

The file name can use relative or absolute paths, or network protocol mode. The Open mode has the r + ww + aa + xx + flag if no B flag is specified when operating the binary file, some strange problems may occur, including bad image files and strange characters.

For portability considerations, we strongly recommend that you always use the B flag when opening a file with fopen.

There are several ways to open files:

$ Fp = @fopen(log.txt, "rb ");

$ Fp = @ fopen (../log.txt, "rb ");

$ Fp = @ fopen ("http://www.runer.com.cn/default.htm", "rb"); // You can also use protocols such as ftp and ghoper, which must enable the allow_url_fopen option in the php. ini file

/// // Code ////////// //////////////////////////////

$ Filename1 = "userinfo.txt"; // The file exists in the directory or in include_path.

$ Filename2 = "test.txt"; // The file does not exist in the directory or in include_path.

$ Resource1 = fopen ($ filename1, "rb ");

@ $ Resource2 = fopen ($ filename2, "rb"); // This Operation returns an error because the file does not exist in the directory and is not used or because de_path is used to find the path containing the file, use the error blocker @ to force the browser not to output error messages

If ($ resource1)

Echo "opening file {$ filename1} succeeded ";

If (! @ Fopen ($ filename2, "r "))

Echo "opening file {$ filename2} failed ";

//////////////////////////////////////// //////////////////////////////////

--------------------- Output result ----------------------------------------

The userinfo.txt file is successfully opened.

---------------------------------------------------------------------

2. after using the file, you must explicitly tell PHP that the file has been used, so that the operating system can ensure that all the content of the file is correctly refreshed from the buffer to the hard disk.

Use fclose () to close the file,

Bool fclose (resource handle) // close an opened file pointer

3. read files. the mode parameter of the fopen function can be read. PHP provides several functions to read data from files.

String fgets (int handle [, int length]) reads a row from the file pointer. if you try fgets in a binary file, unpredictable results are generated.

If the length is not specified, 1 K of data is read by default, and stops when a line break (including in the returned value), EOF, or length-1 bytes have been read.

String fgetss (resource handle [, int length [, string allowable_tags]) read a row from the file pointer and filter out the HTML tag

Fgetc () reads a single character

Fread () reads arbitrary binary data

/// // Code ////////// //////////////////////////////

$ Handle = fopen ("test.jpg", "rb ");

$ C;

While (! Feof ($ handle )){

$ Contents. = @ fread ($ handle, 8192); // read it cyclically and merge it into a large file.

}

Fclose ($ handle );

//////////////////////////////////////// //////////////////////////////////

--------------------- Output result ----------------------------------------

---------------------------------------------------------------------

4. determine the file reading status

Each file handle has a file pointer, or a cursor indicating where the next operation will occur in the file. according to the mode parameter of the fopen function

The file pointer is initially at the beginning of the file (0), or at the end of the file

Feof () can be used to determine whether the object has reached the end (the function returns TRUE after the end)

Filesize () function returns the size of the file 5. write the file

Fwrite () function execution file write

/// // Code ////////// //////////////////////////////

$ Filename = test.txt;

$ Somec;

// First, make sure that the file exists and is writable.

If (is_writable ($ filename )){

// In this example, we will use the add mode to open $ filename,

// Therefore, the file pointer will start with the file,

// That is where $ somecontent will be written when we use fwrite.

If (! $ Handle = fopen ($ filename, )){

Echo "the file $ filename cannot be opened ";

Exit;

}

// Write $ somecontent to the open file.

If (fwrite ($ handle, $ somecontent) === FALSE ){

Echo "cannot be written to file $ filename ";

Exit;

}

Echo "successfully writes $ somecontent to the file $ filename ";

Fclose ($ handle );

} Else {

}

Echo "file $ filename cannot be written ";

//////////////////////////////////////// //////////////////////////////////

--------------------- Output result ----------------------------------------

The text is successfully added to the file and written to the file test.txt.

---------------------------------------------------------------------

For binary data, the third parameter must be specified, which contains the number of data bytes written to the disk.

$ Result = @ fwrite ($ fp, $ binary_data, mb_strlen ($ binary_data, 8bit ));

6. file permissions and other information

Is_readable () // checks whether the object is readable.

Is_writeable () // determines whether a file can be written.

Is_writable () // determines whether a file can be written.

Fileperms () // Determine the file permission (UNIX-style file permission test function)

File_exists () // whether the file exists

Fileowner () // determines the user to which the file belongs

Filegroup () // Determine the group to which the file belongs

7. delete and rename an object

Unlink () // delete an object

Rename () // rename the file

8. access the Directory

Forward slash (/) is recommended for directory access. it is compatible with windows and unix systems.

Basename () // returns the file name that does not contain the path information

Dirname () // return the directory part of the file name

Realpath () // accepts the relative path and returns the absolute path of the object.

Pathinfo () // extract the directory name, basic file name, and extension of the specified path

Opendir () // open the directory and return the resource handle

Readdir () // read the directory item

Rewinddir () // returns the start of the Read pointer

Closedir () // Close the read handle

Chdir () // change the current working directory during the execution of the current script

Mkdir () // create a directory

Rmdir () delete directory

/// // Code ////////// //////////////////////////////

//////////////////////////////////////// //////////////////////////////////

--------------------- Output result ----------------------------------------

Filename: web: filetype: dir

Filename: study: filetype: di

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