The usual variables are named by the following statements:
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$a = ' Hello ';
?>
A mutable variable name refers to the use of a variable's value as the name of the variable. In the example above, by using two $ symbols, you can set the hello to a variable name, as in the following.
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$ $a = ' world ';
?>
With the above two statements, two variables are defined: The variable $ A, the contents are "Hello" and the variable $hello, the content is "world". So, the following language:
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echo "$a ${$a}";
?>
Exactly the same as the output of the following statement:
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echo "$a $hello";
?>
They all output: Hello world.
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.
Example 1 variable variable name
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class Foo {
var $bar = ' I am bar ';
}
$foo = new Foo ();
$bar = ' Bar ';
$baz = Array (' foo ', ' Bar ', ' baz ', ' Quux ');
$bar Echo $foo. "N";
$baz echo $foo [1]. "N";
?>
The above example will output the following results:
I am Bar.
I am Bar.
Warning
Note that 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.
The above describes the use of the COUNTIF function of PHP variable name of the use of methods to share, including the use of the COUNTIF function of the content, I hope that the PHP tutorial interested in a friend helpful.
