src/Zend/Filter/File/UpperCase.php
public function filter($value)
    {
        if (!file_exists($value)) {

            throw new Zend_Filter_Exception("File '$value' not found");
        }

        if (!is_writable($value)) {

            throw new Zend_Filter_Exception("File '$value' is not writable");
        }

        $content = file_get_contents($value);
        if (!$content) {

            throw new Zend_Filter_Exception("Problem while reading file '$value'");
        }

        $content = parent::filter($content);
        $result  = file_put_contents($value, $content);

        if (!$result) {

            throw new Zend_Filter_Exception("Problem while writing file '$value'");
        }

        return $value;
    }
public function filter($value)
    {
        if (!file_exists($value)) {

            throw new Zend_Filter_Exception("File '$value' not found");
        }

        if (!is_writable($value)) {

            throw new Zend_Filter_Exception("File '$value' is not writable");
        }

        $content = file_get_contents($value);
        if (!$content) {

            throw new Zend_Filter_Exception("Problem while reading file '$value'");
        }

        $content = parent::filter($content);
        $result  = file_put_contents($value, $content);

        if (!$result) {

            throw new Zend_Filter_Exception("Problem while writing file '$value'");
        }

        return $value;
    }
Defined by Zend_Filter_Interface

Does a lowercase on the content of the given file

@param  string $value Full path of file to change
@return string The given $value
@throws Zend_Filter_Exception