PHP variable Variable instance details

What is a mutable variable?

There is one other type of variable in PHP, "mutable variable." A mutable variable is a unique variant of PHP that allows you to dynamically change the name of a variable.

How mutable variables work

This feature works by using the value of one variable as the name of another variable. For example, we can set the value of $STR:
$name = ' str ';
So, we can use

Name replaces $str.

name = 5;
This code is equivalent to:
$STR = 5;

How to use

Using mutable variables is to add a dollar sign "$" to the front of the variable.

Arrays using mutable variables

In order to use the variable variable name of the array, you need to solve a ambiguity problem. That is, if you write $ $a [1], the parser needs to know whether you mean to use $a[1] as a variable, or to use the $ $a as a variable, [1] to refer to the index of the variable. The syntax for solving this ambiguity is: The first case uses ${$a [1]}, and the second case uses ${$a}[1]

Class properties can also be accessed through variable property names. A mutable property name is obtained from the access scope of the variable where the call is generated. For example, if your expression is this: $foo-$bar, the runtime will look for the variable $bar within the scope of the local variable, and its value will be a property name for the $foo object. If the $bar is an array, it can be used.

mutable variable names cannot be used on PHP functions and super Global array variables in classes. Variable $this is also a special variable that cannot be named dynamically.

Instance

The following instance uses a mutable variable to change the name of the variable. The code is as follows:

<?phpheader ("Content-type:text/html;charset=utf-8");                Set the encoding $str= ' trans ';                                                  Declaring variable $str$trans= ' topic.alibabacloud.com ';                                            declaring variable $transecho $str;                                                     Output variable $strecho "<br/>"; echo $ $str;                                                 Output the value of $trans through a mutable variable?>

Detailed Examples:

First define two variables $str and $trans, and output the value of the variable $str, then use the variable variable to change the name of the variable $str, and finally output the variable value after the change name

The results of the operation are as follows:

The above is a simple use of mutable variables, the next section, for you to introduce "pre-defined PHP variables"

Related video tutorial recommended: "Php.cn lonely Nine Cheap (4)-php video tutorial" mutable variable: Provides a new way to create new variables