[英]Curly Braces Notation in PHP
I was reading source of OpenCart and I ran into such expression below. 我正在阅读OpenCart的源代码,并且在下面遇到了这种表达。 Could someone explain it to me:
有人可以向我解释一下:
$quote = $this->{'model_shipping_' . $result['code']}->getQuote($shipping_address);
In the statement, there is a weird code part that is 在语句中,有一个奇怪的代码部分是
$this->{'model_shipping_' . $result['code']}
which has {}
and I wonder what that is? 哪个有
{}
,我想知道是什么吗? It looks an object to me but I am not really sure. 对我来说,这似乎是一个对象,但我不确定。
Curly braces are used to denote string or variable interpolation in PHP. 花括号用于表示PHP中的字符串或变量插值。 It allows you to create 'variable functions', which can allow you to call a function without explicitly knowing what it actually is.
它允许您创建“变量函数”,这可以使您在不显式知道函数实际含义的情况下调用该函数。
Using this, you can create a property on an object almost like you would an array: 使用此方法,可以像在数组上一样在对象上创建属性:
$property_name = 'foo';
$object->{$property_name} = 'bar';
// same as $object->foo = 'bar';
Or you can call one of a set of methods, if you have some sort of REST API class: 或者,如果您具有某种REST API类,则可以调用一组方法之一:
$allowed_methods = ('get', 'post', 'put', 'delete');
$method = strtolower($_SERVER['REQUEST_METHOD']); // eg, 'POST'
if (in_array($method, $allowed_methods)) {
return $this->{$method}();
// return $this->post();
}
It's also used in strings to more easily identify interpolation, if you want to: 如果要执行以下操作,还可以在字符串中使用它来更轻松地识别插值:
$hello = 'Hello';
$result = "{$hello} world";
Of course these are simplifications. 当然,这些只是简化。 The purpose of your example code is to run one of a number of functions depending on the value of
$result['code']
. 示例代码的目的是根据
$result['code']
的值运行许多函数之一。
The name of the property is computed during runtime from two strings 该属性的名称是在运行时根据两个字符串计算得出的
Say, $result['code']
is 'abc'
, the accessed property will be 假设
$result['code']
为'abc'
,则访问的属性为
$this->model_shipping_abc
This is also helpful, if you have weird characters in your property or method names. 如果属性或方法名称中包含怪异字符,这也很有用。
Otherwise there would be no way to distinguish between the following: 否则,将无法区分以下内容:
class A {
public $f = 'f';
public $func = 'uiae';
}
$a = new A();
echo $a->f . 'unc'; // "func"
echo $a->{'f' . 'unc'}; // "uiae"
Curly braces are used to explicitly specify the end of a variable name.
花括号用于显式指定变量名的结尾。
https://stackoverflow.com/a/1147942/680578 https://stackoverflow.com/a/1147942/680578
http://php.net/manual/en/language.types.string.php#language.types.string.parsing.complex http://php.net/manual/zh-CN/language.types.string.php#language.types.string.parsing.complex
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