php - 可捕获的 fatal error : Object of class "" could not be converted to string in "" on line ""

Question

我有这个代码:

class Date_Time{
private static $month;
private static $year;
private static $day;

public function Date_Time($format){
    return self::getDate($format);
}

public static function getDate($date_format){
    return self::replace_date_string($date_format);
}

public static function replace_date_string($string){
    if(preg_match("/m/", $string)){
        $string = preg_replace("/m/", self::getMonth(), $string);
    }

    if(preg_match("/Y/", $string)){
        $string = preg_replace("/Y/", self::getYear(), $string);
    }

    return $string;
}

public static function getMonth(){
    return date("m");
}

public static function getYear(){
    return date("Y");
}
}

但是如果我这样打印它:

$date = new Date_Time("Y");
echo $date;

它给我一个错误提示:

Catchable fatal error: Object of class Date_Time could not be converted to string in index.php on line 2

我怎样才能解决这个问题，它不会给我一个错误，是什么导致了这个错误。

Answer 1

添加__toString()方法

public function __toString() {
    return $this->getYear() .'-'. $this->getMonth() .'-'. $this->getDay();
}

当您尝试打印整个对象时需要此方法。

对于 PHP4:

public function toString() {
    return $this->getYear() .'-'. $this->getMonth() .'-'. $this->getDay();
}

并手动调用此方法:

$date = new Date_Time("Y");
echo $date->toString();