What is the explanation for the following syntax?开发者_如何学运维
$var1->$var2 // Note the second $
You are calling a property on $var1
that is named the same as the value of $var2
.
For example:
$var2 = "name";
// The following are equivalent
$var1->name;
$var1->$var2;
$var1
is an object.
$var2
is (possibly) the name of a variable inside $var1
.
If $var2="test";
this is evaluated to:
$var1->test;
You can do this with all sorts of things:
$test = array();
$name="test";
print_r($$name); // Prints array();
$test = new stdClass;
$test->hello = "hi";
$name2="hello";
echo $test->$name2; // Echos hi
You can even get really fancy:
echo $$name->$name2; // Echos hi
It means dynamically query a property in an object.
class A {
public $a;
}
// static property access
$ob = new A;
$ob->a = 123;
print_r($ob);
// dynamic property access
$prop = 'a';
$ob->$prop = 345; // effectively $ob->a = 345;
print_r($ob);
so $var1
is an instance of some object, ->
means access to a member of that object and $var2
contains the name of a property.
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