PHP function introduction—is_readable(): Check whether the file is readable

PHP function introduction—is_readable(): Check whether the file is readable

In PHP, we often need to read files. However, before reading the file, we need to ensure that the file is readable, which is a common file processing task. PHP provides a very useful function - is_readable(), which is used to check whether the file is readable.

The basic syntax of the is_readable() function is as follows:

bool is_readable ( string $filename )

Among them, $filename is the file name to be checked for readability.

The return value of the is_readable() function is a Boolean value. If the file is readable, it returns true, otherwise it returns false. Below is a simple example that demonstrates how to use the is_readable() function to check if a file is readable.

<?php
$filename = 'sample.txt';

if (is_readable($filename)) {
    echo "文件可读";
} else {
    echo "文件不可读";
}
?>

In the above example, we checked a file named sample.txt using the is_readable() function. If the file is readable, "File Readable" will be output, otherwise "File Unreadable" will be output.

In addition to a simple file name, the is_readable() function can also accept the absolute path or relative path of the file as a parameter. For example:

<?php
$filename = 'path/to/sample.txt';

if (is_readable($filename)) {
    echo "文件可读";
} else {
    echo "文件不可读";
}
?>

In the above example, we have used the file name with the path as parameter to check whether the file under the specified path is readable.

Note that before using the is_readable() function, you need to ensure that the file to be checked exists. Otherwise, the function will always return false.

In addition, the is_readable() function can also be used to check whether the directory is readable. For example:

<?php
$dirname = 'path/to/directory';

if (is_readable($dirname)) {
    echo "目录可读";
} else {
    echo "目录不可读";
}
?>

In the above example, we checked a directory named path/to/directory using the is_readable() function. If the directory is readable, "Directory Readable" will be output, otherwise "Directory Unreadable" will be output.

It should be noted that the is_readable() function only checks whether the file or directory is readable, but does not check whether it is writable. If you need to check whether a file or directory is writable, use the is_writable() function.

Summary:

The is_readable() function is a very useful PHP function for checking whether a file or directory is readable. It accepts a filename, an absolute path to a file, or a relative path as parameters. The is_readable() function will return true if the file or directory is readable, false otherwise. Before performing file operations, using this function can ensure the safety and stability of the code.

I hope this article can help you better understand and use the is_readable() function.

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