• Lines where some fields are quoted and some aren't
• Lines where quoted fields have 'escaped' quotes inside them
• Lines where non-quoted fields have 'escaped' delimiters inside them
• Lines where the quote is 'escaped' by another quote (the default behaviour for Excel CSV exports)

• Lines containing multi-byte strings

/**
 * Split a line from a CSV file into fields. Should handle various field
 * delimiters, escape characters and enclosing quotes for fields
 *
 * @param string $line Line to split for the CSV
 * @param string $delimiter Field delimiter (defaults to ',')
 * @param string $escaper Field escaper (defaults to '\')
 * @param string $encloser Field encloser (defaults to '"')
 */
    function splitCsvLine($line, $delimiter=',', $encloser='"', $escaper='\\') {
                            
        $fields = array();               
        if (is_string($delimiter) && is_string($encloser)) :
            
            // Make sure the arguments are regex-safe 
            $reg_safe_delimiter = '\x' . dechex(ord($delimiter));
            $reg_safe_encloser = '\x' . dechex(ord($encloser));
            $reg_safe_escaper = '\x' . dechex(ord($escaper));
        
            $line = trim($line);
            
            // Replace any 'quote-escaped' quotes within fields. This is only really necessary to 
            // handle excel exports, which often escape double quotes with double quotes. 
            if ($encloser == $escaper) :
                $line = mb_ereg_replace($reg_safe_escaper . $reg_safe_encloser, "__ESCAPED__ENCLOSER__", $line);
            endif;
            
            // Loop over the string and extract each field       
            $field_num = 0;
            while(mb_strlen($line) > 0) :
                if(mb_substr($line, 0, 1) == $encloser) :
                
                    // If this string starts with an encloser, look for the next (non-escaped) encloser
                    preg_match('/^' . $reg_safe_encloser . '((?:[^' . $reg_safe_encloser . 
                                ']|(?<='.$reg_safe_escaper.')' . $reg_safe_encloser . 
                                ')*)' . $reg_safe_encloser . $reg_safe_delimiter . 
                                '?(.*)$/', $line, $matches);
                    $value = mb_ereg_replace($reg_safe_escaper . $reg_safe_encloser, $encloser, $matches[1]);
                    $line = trim($matches[2]);                   
                    $fields[$field_num++] = $value;
                    
                // Otherwise, look for the next (non-escaped) delimiter
                else :
                    preg_match('/^((?:[^' . $reg_safe_delimiter . 
                                ']|(?<='.$reg_safe_escaper.')' . $reg_safe_delimiter . 
                                ')*)' . $reg_safe_delimiter . 
                                '?(.*)$/', $line, $matches);                   
                    $value = mb_ereg_replace($reg_safe_escaper . $reg_safe_delimiter, $delimiter, $matches[1]);
                    $line = trim($matches[2]);
                    $fields[$field_num++] = $value;
                endif;
            endwhile;
       
            if ($encloser == $escaper) :
                for ($i=0; $i<count($fields); $i++) :    
                    $fields[$i] = mb_ereg_replace("__ESCAPED__ENCLOSER__", $encloser, $fields[$i]);
                endfor;
            endif;
        endif;
            
        return $fields;
    }