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self::get_one_by_sql

先確定下父類的get_one_bysql 是不是靜態(tài)的

關(guān)于使用 https://stackoverflow.com/que...

你這么用的顯然很不規(guī)范, 當(dāng)然先說正題.
要調(diào)父類的非靜態(tài)方法, 首先你得取到類實例
如果有緩存就直接拿, 沒有就創(chuàng)建一個

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

調(diào)用不了.

非靜態(tài)方法需要有$this對象, 從靜態(tài)方法調(diào)用提供不了這個對象.

打開注釋玩玩就知道了

<?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();

總結(jié)：this用于實例調(diào)用。self，parent用于調(diào)用靜態(tài)屬性或方法。
最后一個奇特的現(xiàn)象是雖然靜態(tài)調(diào)用父類的非靜態(tài)方法處理數(shù)據(jù)，會得到一個報錯，但是還是輸出了int(3)