Convert WordPress URL/Slug from lowercase to uppercase.

functions.php

//this for SLUG url lowercase to uppercase
 add_filter( 'sanitize_title', 'wpse5029_sanitize_title_with_dashes', 10, 3 );
function wpse5029_sanitize_title_with_dashes($title, $raw_title, $context = 'display') {

    $title = strip_tags( $raw_title );
    // Preserve escaped octets.
    $title = preg_replace( '|%([a-fA-F0-9][a-fA-F0-9])|', '---$1---', $title );
    // Remove percent signs that are not part of an octet.
    $title = str_replace( '%', '', $title );
    // Restore octets.
    $title = preg_replace( '|---([a-fA-F0-9][a-fA-F0-9])---|', '%$1', $title );

    if ( seems_utf8( $title ) ) {
        $title = utf8_uri_encode( utf8_encode($title), 200 );
    }
    if ( 'save' === $context ) {
        // Convert &nbsp, &ndash, and &mdash to hyphens.
        $title = str_replace( array( '%c2%a0', '%e2%80%93', '%e2%80%94' ), '-', $title );
        // Convert &nbsp, &ndash, and &mdash HTML entities to hyphens.
        $title = str_replace( array( ' ', ' ', '–', '–', '—', '—' ), '-', $title );
        // Convert forward slash to hyphen.
        $title = str_replace( '/', '-', $title );

        // Strip these characters entirely.
        $title = str_replace(
            array(
                // Soft hyphens.
                '%c2%ad',
                // &iexcl and &iquest.
                '%c2%a1',
                '%c2%bf',
                // Angle quotes.
                '%c2%ab',
                '%c2%bb',
                '%e2%80%b9',
                '%e2%80%ba',
                // Curly quotes.
                '%e2%80%98',
                '%e2%80%99',
                '%e2%80%9c',
                '%e2%80%9d',
                '%e2%80%9a',
                '%e2%80%9b',
                '%e2%80%9e',
                '%e2%80%9f',
                // Bullet.
                '%e2%80%a2',
                // &copy, &reg, &deg, &hellip, and &trade.
                '%c2%a9',
                '%c2%ae',
                '%c2%b0',
                '%e2%80%a6',
                '%e2%84%a2',
                // Acute accents.
                '%c2%b4',
                '%cb%8a',
                '%cc%81',
                '%cd%81',
                // Grave accent, macron, caron.
                '%cc%80',
                '%cc%84',
                '%cc%8c',
            ),
            '',
            $title
        );

        // Convert &times to 'x'.
        $title = str_replace( '%c3%97', 'x', $title );
    }
    // Kill entities.
    $title = preg_replace( '/&.+?;/', '', $title );
    $title = str_replace( '.', '-', $title );
    
    $title = preg_replace( '/[^%a-zA-Z0-9 _-]/', '', $title );
    $title = preg_replace( '/\s+/', '-', $title );
    $title = preg_replace( '|-+|', '-', $title );
    $title = trim( $title, '-' );
    
    return $title;
}