This document lists every PHP file function a Web developer will ever need.
As a Web developer, it's common to have to interact with files on disk: check disk usage, read file permissions, find file modification times, and read file contents. Fortunately PHP comes with a full-fledged set of file functions for just this purpose and this document lists them all, together with usage examples (See Table A). Keep reading, you might discover something new!
Table A
Function
|
Explanation
|
Example
|
| filesize($file) |
This function returns the size of a file, in bytes. It's useful to calculate how much space a file occupies on disk.
| <?php // get file size in bytes echo "Size is " . filesize('myfile.html') . " bytes"; ?> |
| fileowner($file) filegroup($file) |
These functions return the owner and group ID for a file. They're useful to find out who "owns" a particular file.
| <?php // get file owner and group echo "UID: " . fileowner('myfile.html'); echo "GID: " . filegroup('myfile.html'); ?> |
| fileatime($file) filemtime($file) |
These functions return a timestamp indicating when a file was last accessed and modified respectively. They're useful to find out if a file has changed since a particular date.
| <?php // get file access/modification times echo "Last accessed on: " . date("d-m-y", fileatime('myfile.html')); echo "Last modified on: " . date("d-m-y", filemtime('myfile.html')); ?> |
| fileperms($file) |
This function returns the permissions of a file. Use it to check if a file is readable, writable or executable.
| <?php // get permissions in octal format echo "File permissions: " . sprintf('%o', fileperms('myfile.html')); ?> |
| filetype($file) |
This function returns the "type" of a file - whether link, directory, character or block device, or regular file. Use this to test the nature of a file before using it in an operation.
| <?php // get file type echo "File type: " . filetype('myfile.html'); ?> |
| stat($file) |
This function is a "catch all" function that returns detailed statistics about a file, including its owner and group, size, time of last change, block usage and inode number. Use this function instead of the functions listed previously if you need to obtain complete file statistics in a single call.
| <?php // get file statistics print_r(stat('myfile.html')); ?> |
| realpath($file) |
This function turns a relative file path into an absolute path. It's useful when you need to find out exactly where a file is located on disk.
| <?php // get absolute path // returns "/tmp/myfile.html" echo "File path: " . realpath("./cook/book/../../myfile.html"); ?> |
| basename($file) dirname($path) |
Given a complete file path, these functions can split it into its constituent parts and separately return the file name and directory name respectively.
| <?php // split directory and file names // returns "/usr/local/bin" echo "Directory: " . dirname("/usr/local/bin/php"); // returns "php" echo "File: " . basename("/usr/local/bin/php"); ?> |
| file($file) |
This function reads the contents of a file into an array. Each element of the array represents one line of the file. This function is useful to read a file's contents into a variable, so that it can be processed further.
| <?php // read file contents $lines = file('myfile.html'); // print line by line for($x=1; $x<=sizeof($lines); $x++) { echo "Line $x: " . $lines[$x-1] . "\n"; } ?> |
