All 7 File Handling & File System Functions questions
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How do you read the contents of a file in PHP using functions like file_get_contents and fopen? How do you write data to a file in PHP, and what is the difference between overwriting a file and appending to it? How do you work with directories in PHP, including listing their contents, creating new directories, and recursively deleting them? How do file locking mechanisms in PHP, using the flock function, help prevent data corruption when multiple processes might write to the same file concurrently? How do stream wrappers and stream contexts in PHP allow file functions to work seamlessly with non local resources like remote URLs or cloud storage? What security risks are associated with file handling operations that involve user supplied file paths, and how does path traversal attack prevention work?
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PHP › File Handling & File System Functions

How do you check whether a file or directory exists, and how do you retrieve useful metadata like a file's size or last modified time?

Intermediate

Answer

The file_exists function checks whether a given path exists as either a file or a directory, while functions like filesize and filemtime retrieve specific metadata about a file, such as its size in bytes and the timestamp it was last modified, all of which are commonly used to validate assumptions before performing an operation, such as confirming a required configuration file actually exists before attempting to read it.
if (file_exists('config.php')) {
    echo 'Last modified: ' . date('Y-m-d', filemtime('config.php'));
}
Real-world example An application checks whether a specific uploaded file already exists before allowing a user to upload another file with the same name, preventing an accidental overwrite of previously uploaded content.

Common follow-ups: What is the difference between file_exists and is_file for checking specifically for a file rather than a directory?;How do you retrieve a file's permissions using PHP?

File Upload Handling;Security
All 7 File Handling & File System Functions questions