UniqueFileName.php

<?php

/**
 * UniqueFileName
 * Check whether file exists in path, and build unique name for them
 */
class UniqueFileName
{
    /**
     * @var string path to directory where file suppose to be located
     */
    protected $path;

    /**
     * @param string $path path to directory with trailing slash
     */
    public function __construct($path) {
        $lastChar = substr($path, -1);
        if ($lastChar !== DIRECTORY_SEPARATOR) {
            throw new Exception("Path should contain trailing slash!");
        }
        $this->path = $path;
    }

    /**
     * Build new name for file i.e. AAA.png -> AAA_1.png
     * @param string $fileName file name with extension
     * @return string new file name
     */
    public function buildName($fileName) {
        if (!$this->fileExists($fileName)) {
            return $fileName;
        }
        $fileNameArray = explode(".", $fileName);
        $extension = array_pop($fileNameArray);
        $counter = 0;
        $baseName = implode(".", $fileNameArray);
        do {
            $counter++;
            $newName = $baseName . "_{$counter}." . $extension;
        } while ($this->fileExists($newName));
        return $newName;
    }

    /**
     * 
     * @param string $fileName whether file exist
     * @return bool
     */
    protected function fileExists($fileName) {
        return file_exists($this->path . $fileName);
    }
}