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A variable of a variable takes a value of a variable and threads which is the name of a variable. This is new feature of using variables and by using double dollar signs. This technique is called a dynamic variable in PHP. Those variables you can use a dynamically generated variable of variable as well as OOP Concept.
The $x (single dollar) is the normal variable with the name x that stores any value like string, integer, float, etc. The $$x (double dollar) is a reference variable that stores the value which can be accessed by using the $ symbol before the $x value. These are called variable variables in PHP.
A variable name must start with a letter or the underscore character. A variable name cannot start with a number. A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ) Variable names are case-sensitive ( $age and $AGE are two different variables)
A variable in PHP is a name of memory location that holds data. In PHP, a variable is declared using $ sign followed by variable name. The main way to store information in the middle of a PHP program is by using a variable. Here are the most important things to know about variables in PHP.
Wrap them in {}:
${"file" . $i} = file($filelist[$i]);
Using ${} is a way to create dynamic variables, simple example:
${'a' . 'b'} = 'hello there';
echo $ab; // hello there
In PHP, you can just put an extra $ in front of a variable to make it a dynamic variable :
$$variableName = $value;
While I wouldn't recommend it, you could even chain this behavior :
$$$$$$$$DoNotTryThisAtHomeKids = $value;
You can but are not forced to put $variableName between {} :
${$variableName} = $value;
Using {} is only mandatory when the name of your variable is itself a composition of multiple values, like this :
${$variableNamePart1 . $variableNamePart2} = $value;
It is nevertheless recommended to always use {}, because it's more readable.
Another reason to always use {}, is that PHP5 and PHP7 have a slightly different way of dealing with dynamic variables, which results in a different outcome in some cases.
In PHP7, dynamic variables, properties, and methods will now be evaluated strictly in left-to-right order, as opposed to the mix of special cases in PHP5. The examples below show how the order of evaluation has changed.
$$foo['bar']['baz']
${$foo['bar']['baz']}
${$foo}['bar']['baz']
$foo->$bar['baz']
$foo->{$bar['baz']}
$foo->{$bar}['baz']
$foo->$bar['baz']()
$foo->{$bar['baz']}()
$foo->{$bar}['baz']()
Foo::$bar['baz']()
Foo::{$bar['baz']}()
Foo::{$bar}['baz']()
Try using {} instead of ():
${"file".$i} = file($filelist[$i]);
I do this quite often on results returned from a query..
e.g.
// $MyQueryResult is an array of results from a query
foreach ($MyQueryResult as $key=>$value)
{
${$key}=$value;
}
Now I can just use $MyFieldname (which is easier in echo statements etc) rather than $MyQueryResult['MyFieldname']
Yep, it's probably lazy, but I've never had any problems.
Tom if you have existing array you can convert that array to object and use it like this:
$r = (object) $MyQueryResult;
echo $r->key;
Try using {} instead of ():
${"file".$i} = file($filelist[$i]);
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