PHP $此变量 [英] PHP $this variable

问题描述

我正在阅读一些我不理解的PHP代码:

I am reading some PHP code that I could not understand:

class foo {
  function select($p1, $dbh=null) {
    if ( is_null($dbh) )
        $dbh = $this->dbh ; 
    return; 
  }

  function get() {
    return $this->dbh; 
  }
}

我从类中找不到$this->dbh ($dbh)声明.我的问题是:

I can't find $this->dbh ($dbh) declaration from the class. My questions are:

• $this->dbh的值是什么?

它是函数select()的局部变量吗?

Is it a local variable for function select()?

$this是否属于class foo的数据成员?为什么在此类中没有$dbh的声明?

Does $this belong class foo's data member? Why is there no declaration for $dbh in this class?

推荐答案

PHP对要求类属性声明并不严格.

PHP is not strict about requiring class property declarations.

• 根据赋值，该属性将以静默方式创建.
• 从读取不存在的属性会生成一个通知，如果启用了E_STRICT.
• 任何未定义属性的默认值为NULL

• Upon assignation, the property is silently created.
• Reading from a non-existent property generates a Notice if E_STRICT is enabled.
• The default value for any undefined property is NULL

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