Trim a string in WordPress to a specified number of characters, gracefully stopping at white spaces.

trim_characters

/**
 * Trims a string of words to a specified number of characters, gracefully stopping at white spaces.
 * Also strips HTML tags, to prevent breaking in the middle of a tag.
 *
 * @param	string $text  The string of words to be trimmed.
 * @param	int $length  Maximum number of characters; defaults to 45.
 * @param	string $append  String to append to end, when trimmed; defaults to ellipsis.
 *
 * @return	String of words trimmed at specified character length.
 *
 * @author c.bavota
 */
function trim_characters( $text, $length = 45, $append = '…' ) {

    $length = (int) $length;
    $text = trim( strip_tags( $text ) );

    if ( strlen( $text ) > $length ) {
        $text = substr( $text, 0, $length + 1 );
        $words = preg_split( "/[\s]| /", $text, -1, PREG_SPLIT_NO_EMPTY );
        preg_match( "/[\s]| /", $text, $lastchar, 0, $length );
        if ( empty( $lastchar ) )
            array_pop( $words );

        $text = implode( ' ', $words ) . $append;
    }

    return $text;
}