is_readable()

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The PHP is_readable function is an essential tool that helps you validate file readability before attempting operations like reading or including files. In this guide, we will explore how is_readable works, its syntax, and how to use it. So let's get started.

What Is PHP is_readable?

The is_readable function checks if a given file or directory exists and whether it can be read. It is a built-in PHP function that returns a boolean value—true if the file is readable and false otherwise.

Here is its syntax:

is_readable(string $filename)
  • Parameter: $filename is the file or directory path you want to check.
  • Return Value: The function returns true if the specified file or directory exists and is readable; otherwise, it returns false.

For example:

$file = 'example.txt';

if (is_readable($file)) {
    echo "File is readable.";
} else {
    echo "File cannot be read.";
}

The example above shows that is_readable validates if example.txt is readable. This simple check guarantees that your application will not suffer any surprising errors. Similarly, in the following part:

In the next section, we will see more examples for is_readable.

Examples of PHP is_readable

Validating a File Before Reading

Suppose you want to read a configuration file. Before doing that, you can check if it is readable:

$configFile = 'config.json';

if (is_readable($configFile)) {
    $content = file_get_contents($configFile);
    echo "Configuration loaded successfully.";
} else {
    echo "Cannot access the configuration file.";
}

This ensures your script doesn’t crash if the file is missing or inaccessible.

Ensuring Dynamic Includes Work

When your application dynamically includes files, is_readable verifies the file’s existence and readability:

$fileToInclude = 'plugin.php';

if (is_readable($fileToInclude)) {
    include $fileToInclude;
} else {
    echo "Plugin file not found.";
}

Handling Directory Readability

You have to know that the function is not limited to files—it also works with directories. For example: Here is a check if a directory is accessible before listing its contents:

$directory = 'uploads';

if (is_readable($directory)) {
    echo "Directory is accessible.";
} else {
    echo "Directory cannot be read.";
}

Let's summarize it.

Wrapping It Up

The PHP is_readable function is a way to ensure file and directory accessibility in your applications. By checking readability before performing operations, you can prevent errors, improve security, and provide a smoother user experience.

Thank you for reading. Click here to see more tutorials for PHP. Happy Coding!

Frequently Asked Questions (FAQs)

  • What is PHP 'is_readable' used for?

    PHP is_readable is used to check if a file or directory exists and is accessible for reading. It returns true if the file is readable and false otherwise.

  • How does 'is_readable' differ from 'file_exists'?

    While file_exists only checks if a file or directory exists, is_readable ensures that it is both present and accessible for reading.

  • Can 'is_readable' be used with directories?

    Yes, is_readable works for both files and directories. It verifies if the specified directory exists and can be accessed for reading.

  • What value does 'is_readable' return?

    The is_readable function returns true if the file or directory is readable and false if it is not.

  • Does 'is_readable' follow symbolic links?

    Yes, is_readable follows symbolic links and checks the readability of the target file or directory.

  • How do I use 'is_readable' to avoid file permission errors?

    You can use is_readable to verify a file's accessibility before attempting to read it: 
    $file = 'example.txt';

if (is_readable($file)) {
    $content = file_get_contents($file);
    echo "File content loaded successfully.";
} else {
    echo "Cannot read the file.";

  • Can 'is_readable' check network file access?

    Yes, but the network drive or filesystem must be accessible. If the network resource is temporarily unavailable, is_readable will return false.

  • What should I do if 'is_readable' returns 'false' unexpectedly?

    Double-check the file path, permissions, and ownership. Ensure the file exists, the path is correct (absolute or relative), and the current user has the necessary read permissions.

  • Can 'is_readable' improve application security?

    Yes, using is_readable before accessing files helps prevent your application from trying to process files that are missing or restricted, reducing the risk of unexpected errors and vulnerabilities.
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