我已经尝试了几个小时修复以下方法的bug，不知道为什么它总是返回字符串而不是整数。

如果存在，则返回一个类属性；如果不存在，则返回一个临时值（并为下一次访问设置类属性）。

public static function get_number( $post_id = null ) {
    // Check if class property already exists
    if ( empty( self::$number ) ) {

        // THIS IS ALWAYS STRING - WHY?
        $number = get_transient( \'my_number\' );

        if ( false === $number && $post_id ) {
            $number = get_post_meta( $post_id, \'my_number\', true );

            if ( \'\' !== $number ) {
                $number = intval( $number );
                // THERE GOES THE INTEGER
                set_transient(\'my_number\', $number, 20 );
            }
        }

        self::$number = $number;
        // Should still be an integer since we\'ve never set any strings to transient
    }

    return self::$number;
}

所以
gettype( get_number( 123 ) ) === \'integer\'
gettype( get_number() ) === \'string\'

Working Code (based on Otto\'s answer)

public static function get_number( $post_id = null ) {
    // Check if class property already exists
    if ( empty( self::$number ) ) {

        // THIS IS ALWAYS STRING - WHY?
        $number = get_transient( \'my_number\' );

        if ( false === $number && $post_id ) {
            $number = get_post_meta( $post_id, \'my_number\', true );

            if ( \'\' !== $number ) {
                // THERE GOES AN ARRAY OF THE INTEGER
                set_transient(\'my_number\', array( intval( $number ) ), 20 );
                self::$number = intval( $number );
                return intval( $number );
            }
        }

        self::$number = isset( $number[ 0 ] ) ? $number[ 0 ] : \'\';
    }

    return self::$number;
}