php invoke class instance from dynamically generated string

Question

lets say I have a class named 'translations'. I have an instance of the class called 'chinese_translations'

$chinese_translations = new translations;

Afterwards, I want to call this instance from a dynamically built string and I have tried several ways:

$part1 = 'chinese_';
$part2 = 'translations';
$instance_of_translations = ${$part1.$part2};
$instance_of_translations->getMsg();//Doesn't work

Also like this:

$part1 = 'chinese_';
$part2 = 'translations';
$instance_of_translations = $part1.$part2;
$$instance_of_translations->getMsg();//Doesn't work

I always get the "Call to a member function getMsg() on a non-object" message. What I'm doing wrong?

*SOME ACTIONS TAKEN AND RESULTS OBTAINED:

//Lets see if the var is in scope:

echo $chinese_translations->getMsg(get_locale());//It works

$instance_of_translations = ${$part1.$part2};//Let's try to build the name dynamically

echo $chinese_translations->getMsg(get_locale()); //Call to a member function getMsg() on a non-object

echo $$chinese_translations->getMsg(get_locale()); //Object of class internal_message could not be converted to string in

var_dump($instance_of_translations);//It throws the following:

//object(internal_message)#1956 (1) { ["message"]=> array(2) { ["es_ES"]=> string(19) "The expected result" ["it_IT"]=> string(19) "The expected result" } }NULL

Your first example is working on my computer. Are you sure that the $chinese_translations is in the same scope like the part where you are calling getMsg()? — mario.van.zadel
– mario.van.zadel, Commented Feb 1, 2016 at 12:24

axiac · Accepted Answer · 2016-02-01 12:20:17Z

2

$part1.$part2 is a string. Therefore, $instance_of_translations is the variable name, not the variable itself.

Try this:

$part1 = 'chinese_';
$part2 = 'translations';
$varName = $part1.$part2;
$instance_of_translations = $$varName;
var_dump($instance_of_translations);

It should reveal an object of type translations.

3 Comments

user997593 Over a year ago

This way I get the following output: "Class name must be a valid object or a string"

axiac Over a year ago

Both versions of your code work, mine works too. 3v4l.org/QhHmP Maybe you have a variable scope issue (f.e. $instance_of_translations is a global variable and you try to access it in a function or method.)

user997593 Over a year ago

There was an scope issue, sorry for your waste of time and thanks for your help!

Kaiser · Accepted Answer · 2016-02-01 12:19:37Z

1

try this:

$className = $part1.$part2;
$instance = new $$className;
$instance->getMsg();

answered Feb 1, 2016 at 12:19

Kaiser

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Comments

user997593 · Accepted Answer · 2016-02-01 16:21:52Z

0

Finally the bracket version did the trick, but there was an scope issue so both answer maybe right. This one:

 $part1 = 'chinese_';
 $part2 = 'translations';
 $instance_of_translations = ${$part1.$part2};
 $instance_of_translations->getMsg();

Is currently working for me.

answered Feb 1, 2016 at 16:21

user997593

4335 silver badges16 bronze badges

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