self::get_one_by_sql

先确定下父类的get_one_bysql 是不是静态的

关于使用 https://stackoverflow.com/que...

你这么用的显然很不规范, 当然先说正题.
要调父类的非静态方法, 首先你得取到类实例
如果有缓存就直接拿, 没有就创建一个

$instance = new self();
$totalCount = $instance->get_one_bysql($sqlstr);

调用不了.

非静态方法需要有$this对象, 从静态方法调用提供不了这个对象.

打开注释玩玩就知道了

<?php
class a{
    public $ab = NULL;
    public function d(){
        var_dump($this->ab);
    }
    public function c($a,$b){
        var_dump($a+$b);
    }
}

class b extends a{
    public static function t(){
        // $this->d();          //Fatal error: Using $this when not in object context in D:\phpStudy\WWW\index.php on line 14
        // $this->c(1,2);          //Fatal error: Using $this when not in object context in D:\phpStudy\WWW\index.php on line 15
        // self::d();             //Strict Standards: Non-static method a::d() should not be called statically in D:\phpStudy\WWW\index.php on line 16
                                //Fatal error: Using $this when not in object context in D:\phpStudy\WWW\index.php on line 5
        // self::c(1,2);        //Strict Standards: Non-static method a::c() should not be called statically in D:\phpStudy\WWW\index.php on line 18 
                                // int(3)
        // parent::d();            //Strict Standards: Non-static method a::d() should not be called statically in D:\phpStudy\WWW\index.php on line 20
                                // Fatal error: Using $this when not in object context in D:\phpStudy\WWW\index.php on line 5
        // parent::c(1,2);        //Strict Standards: Non-static method a::c() should not be called statically in D:\phpStudy\WWW\index.php on line 22
                                //int(3)
    }
}
b::t();

总结：this用于实例调用。self，parent用于调用静态属性或方法。
最后一个奇特的现象是虽然静态调用父类的非静态方法处理数据，会得到一个报错，但是还是输出了int(3)