Using PHP filetype() Function to Determine File Types

In PHP, the filetype() function is a built‑in function used to determine the type of a file, returning the file type information quickly for further processing or decision making.

Function prototype: string filetype ( string $filename ) Parameter: $filename – the name or path of the file to be examined.

Return value: If the file type is successfully identified, the function returns its type as a string; otherwise it returns false.

Example 1: Get a file’s type

$filename = 'example.txt';

$filetype = filetype($filename);

if ($filetype !== false) {
    echo "文件的类型为：" . $filetype;
} else {
    echo "获取文件类型失败！";
}

This example defines a file name ( example.txt), calls filetype() to obtain its type, and echoes the result if the call does not return false.

Example 2: Get types of all files in a directory

$dir = 'example_folder/';

$files = scandir($dir);

foreach ($files as $file) {
    if ($file != "." && $file != "..") {
        $filepath = $dir . $file;
        $filetype = filetype($filepath);
        if ($filetype !== false) {
            echo "文件 {$file} 的类型为：" . $filetype . "<br/>";
        } else {
            echo "获取文件类型失败！";
        }
    }
}

This example lists all entries in example_folder/ using scandir(), iterates over each file (skipping . and ..), calls filetype() for each path, and outputs the type or an error message.

Summary: The filetype() function is a convenient tool for retrieving file type information in PHP, enabling developers to handle different file types appropriately—such as resizing images or processing text files—based on the returned type.