Master PHP’s is_file(): Quick Guide to Checking File Existence

is_file()

is a basic and useful PHP function that checks whether a specified file exists.

The function takes a file path (absolute or relative) as its argument and returns true if the file exists, otherwise false.

Example usage:

$file = '/path/to/myfile.txt';
if (is_file($file)) {
    echo "文件存在";
} else {
    echo "文件不存在";
}

The path can be absolute or relative to the script’s directory; using paths relative to the script’s root is recommended.

Note that is_file() only checks files, not directories. To test a directory, use is_dir().

Because the return value is boolean, it is typically used in if statements, e.g., before calling file_get_contents() to read a file.

$file = '/path/to/myfile.txt';
if (is_file($file)) {
    $content = file_get_contents($file);
} else {
    echo "文件不存在";
}

Additional considerations: if the argument is a symbolic link, is_file() returns true only when the target file exists; it always returns false for directories.

In summary, mastering is_file() helps PHP developers avoid errors when handling file operations.