PHP Variable Variable inside []'s - php

Question

Thanks for the help below, however, I'm still having some problems, I'll try and explain further:
I have a variable as follows:
$value['questions'];
Now, I need to do a check in a loop, so I have this piece of code in the loop:
if($results[$value['questions']]==4){blah blah blah};
but the problem I am having is that the value of $value['questions'] is q1 but I need the q1 to be a string (i.e. inside quotes '') in the $results section of the code, so the $results element should look like this...
if($results['q1']==4){blah blah blah};
currently it looks like this
if($results[q1]==4){blah blah blah};
Make sense?
Thanks again for the help.
Hi all,
I hope there is a simple solution!
I have a variable:
$results['q1'];
Is it possible to have the 'q1' element as a variable, something like this:
$results['$i[question]'];
Have not been able to find a solution on Google and researching the PHP manuals...
Anyone got a suggestion/ solution?
Thanks,
Homer.

Answer 1

Yes, it is possible to use a variable as indice, when accessing an array element.
As an example, consider this portion of code :
$results = array(
'a' => 'sentence a',
'b' => 'hello !',
);
$indice = 'a';
echo $results[$indice];
Which will give the following output :
sentence a
Here, $indice is a quite simple variable, but you could have used whatever you wanted between the [ and ], like, for instance :
functions : $results[ my_function($parameter) ]
array element : $result[ $my_array['indice'] ]
Which seems to be what you want to do ?
object property : $result[ $obj->data ]
...
Basically, you can use pretty much whatever you want there -- as long as it evaluates to a scalar value (i.e. a single integer, string)
In your specific case, you could have $results declared a bit like this :
$results = array(
'q1' => 'first question',
'q2' => 'second question',
);
And $i would be declared this way :
$i = array(
'question' => 'q1'
);
Which means that $i['question'] would be 'q1', and that the following portion of code :
echo $results[ $i['question'] ];
Would get you this output :
first question
Edit : To answer the specific words you used in the title of your question, you could also use what's called variable variable in PHP :
$variable = 'a';
$indice = 'variable';
echo $results[ $$indice ];
Here :
$indice is 'variable'
and $$indice is 'a'
which means you'll get the same output as before
And, of course, don't forget to read the Arrays section of the PHP manual.
The Why is $foo[bar] wrong? paragraph could be of interest, especially, considering the example you firt posted.
Edit after the edit of the OP :
If $value['questions'] is 'q1', then, the two following portions of code :
if($results[$value['questions']]==4){blah blah blah}
and
if($results['q1']==4){blah blah blah}
should do exactly the same thing : with $results[$value['questions']], the $value['questions'] part will be evaluated (to 'q1') before the rest of the expression, and that one will be the same as $results['q1'].
As an example, the following portion of code :
$results = array(
'q1' => 4,
'q2' => 6,
);
$value = array('questions' => 'q1');
if($results[$value['questions']]==4) {
echo "4";
}
Outputs 4.

Answer 2

You can do:
$results[$i['question']];
This will first access the array $i to get the value corresponding to the key 'question'. That value will be used as the key into the array $results.
Your way: $results['$i[question]'];
is actually trying to get the value corresponding to the key '$i[question]' in the array $results. Since the key is in single quote, variable interpolation does not happen and the entire string is treated literally.
Alternatively you can also do:
$results["$i[question]"]; // using double quotes also works.
Example:
$arr1 = array('php' => 'zend', 'java' => 'oracle');
$arr2 = array('p' => 'php', 'j' => 'java');
echo $arr1[$arr2['p']]; // prints zend.
echo $arr1["$arr2[p]"]; // prints zend.

Answer 3

<?php
$result['q1'];
// is equivalent to
$index = 'q1';
$result[ $index ];
Now $index can be as complex as you want it to be. For example something like this is also possible:
$result[ 'q' . round( $someArray[$i] / 2 ) ];

Answer 4

CODE
<?php
$results = array(
'q1' => 'This is a result called q1.',
'q2' => 'So, can you access this?',
'$i[question]' => 'This is a result called $i[question]',
);
$i = array(
'question' => 'q2',
'answer' => 'Yes.'
);
echo '<pre>';
echo $results['q1'] . "\n"; // Using Array's is easy -
echo $results['$i[question]'] . "\n"; // all you gotta do is make sure
echo $results[$i['question']] . "\n"; // that you understand how
echo $i['answer']; // the keys work.
?>
OUTPUT
This is a result called q1.
This is a result called $i[question]
So, can you access this?
Yes.