reference variable array - php

I always use $text = $datasql[0];
where $datasql = array('0'=>array('some'=>'text', 'some2'=>'text2'), '1'=>$data, etc...);
and found work construction $datasql = &$datasql[0]; and work, why?
That really reference?? and how remember php in memory this solution.


Every variable is a reference to a value. Normally the value is copied when you use it, but with & the reference is copied.
Suppose you have the following variable:
$original = 'john';
If you assign the value from $datasql to a variable, that value is copied:
$text = $original;
If you assign a reference, the value is not copied but referenced:
$text = & $original;
This means that $text points to the value of $original. Now, if you unset $original, the contents of $text are still valid:
unset($original);
echo $text; // john
This is because PHP knows there is still a reference to the value of $original, so it deletes the $original variable as name, but not the contents.
Your example is similar, except that the variable is not explicitly unset, but overwritten. It is a reference to a value, just like any other variable.

Related

Get a value from an associative array with $_GET

Say for example that I have this variable
$p0001 = array("title"=>"This is the title","name"=>"Just Me");
And the URL is
https://www.example.com?id=p0001
How do I get the correct array from PHP? I've tried
echo $_GET["id"]["title"];
To explain little more, say I have two array variables. I want it to echo the "title" from from the array $p0001. So how do I make sure I gets the variable I put in $_GET?

You can use Variable variables
So, your variable name is $p0001. Your GET parameter id is basically a pointer to the variable name, so using variable variables, we can reference the variable we're looking for:
$varname = $_GET['id']; // $varname = 'p0001';
$$varname; // this is basically $p0001
$$varname['title']; // and you can get your title from $p0001
You could also check if a variable exists before using with isset($$varname)

Variable without name: ${''}

So variable variables are existing. Meaning that this is working
$a = 'test';
$$a = 'Hello';
echo ${'test'}; //outputs 'Hello'
But now I've come across some rather strange code using a variable without a name:
function test(&$numRows) {
$numRows = 5;
echo ' -- done test';
}
$value = 0;
test($value);
echo ' -- result is '.$value;
test(${''}); //variable without name
http://ideone.com/gTvayV Code fiddle
Output of this is:
-- done test -- result is 5 -- done test
That means, the code is not crashing.
Now my question is: what exactly happens if $numRows value is changed when the parameter is a variable without name? Will the value be written into nirvana? Is that the PHP variable equivalent to /dev/null?
I wasn't able to find anything specific about this.
Thanks in advance

${''} is a valid variable which name happens to be an empty string. If you have never set it before, it is undefined.
var_dump(isset(${''})); // if you have never set it before, it is undefined.
You don't see any error because you disabled the NOTICE error message.
error_reporting(E_ALL);
ini_set('display_errors', 1);
echo ${''}; // Notice: Undefined variable:
You can set it like this:
${''} = 10;
echo ${''}; // shows 10

Now my question is: what exactly happens if $numRows value is changed
when the parameter is a variable without name?
There's no such thing as a variable without name, an empty string in PHP is a totally valid name.
Maybe I'm wrong, but in PHP, all varibles can be accessed by their names (or more precisely, the string representation of their name), and since an empty string is still a string, it counts as a valid name.
Think about variables like an array key-value pair. You can create an array key with an empty string:
$arr = [];
$arr[''] = 'appul';
var_dump($arr['']); // prints: string(5) "appul"
$arr[''] = 'ponka';
var_dump($arr['']); // prints: string(5) "ponka"
Whenever you access $arr[''], you address the same value.
You can access all variables as a string using the $GLOBAL variable too, so you can examine what happens to your "nameless" variable:
${''} = 'ponka';
var_dump($GLOBALS['']); // prints: string(5) "ponka"
${''} = 'appul';
var_dump($GLOBALS['']); // prints: string(5) "appul"
Will the value be written into nirvana? Is that the PHP variable equivalent to /dev/null? I wasn't able to find anything specific about this.
No, it doesn't go to nirvana, it sits quietly in the global space, and it's a little bit trickier to access it, but otherways, it's a normal variable like any others.

Why is zero and alphabet missing when I display the variable in PHP?

I'm new to PHP and I got somebody else's code to work on.
There are multiple variables including $CARD.
But unlike other variables $CARD cannot display a character.
For example, when I input a value like 'passw0rd', all the other variables outputs 'passw0rd'. But the $CARD variable outputs a '0'.
And also, when I take an input like '0123', all the other variables outputs the same '0123'. But only the $CARD variable drops the 0 and outputs '123'.
Is there any PHP elements that I should be suspecting/?

If you see some thing like this in the code. that $CARD variable is cast to int.
$num = "3.14";
$CARD = (int)$num;
You can convert it to string as follows.
$var2 = (string)$CARD;

Setting a value to variable

I have a problem assigning value to a variable in php.
Example what I am trying to do:
Suppose I have 3 variables and I want to assign the value of 3rd variable to 4th variable but in 3rd variable I want to use first 2 variables.
$depth = 1;
$forumcat = _cat;
$f1_cat = 'some html code';
$new = '';
Now I want to assign $f1_cat to $new variable
I know it can be done like $new = $f1_cat but I want to do it like
$new = $f$depth$forumcat;
I mean in place of using '1_cat' I want to use the variables.
I tried the following
$new = "\$f{$depth}{$forumcat}";
but this statement assigns a string $f1_cat but I want to assign $f1_cat variable value.
How to do it?

$new = ${'f'.$depth.$forumcat}; // This will contain value of $f1_cat
Also you may want to change $forumcat = _cat; to $forumcat = '_cat';. please note the single quotes added to _cat

Dynamically created Variables in PHP produce occasionally names like "_GET" or "_POST" instead of the variable names

I have a function from which I call many different variables, and produce another (dynamically created) return variable.
All good. (I explain my Problem below this PHP 5.3 example)
function showArrayIntersection($ar1, $ar2) {
$dynamicName = array_search($ar1, $GLOBALS) . '_' . array_search($ar2, $GLOBALS);
global ${$dynamicName};
${$dynamicName} = implode(array_values(array_intersect($ar1, $ar2)));
}
$Bankers = [6,7,0,6,5,6,2]; // `[]` is equivalent to `array()` introduced in PHP 5.4
$Bond = [6,7,0,5,0];
$Politicians = [4,6,1,6,4,6,3];
$James = [0,1,0,3,7];
showArrayIntersection($James, $Bond);
showArrayIntersection($Bankers, $Politicians);
echo "Moneysystem: $Bankers_Politicians\n";
echo "Moneypenny : $James_Bond\n";
Output:
Moneysystem: 666
Moneypenny : 007
This works most of the time well, but sometimes only instead of a variable name like $James_Bond I get a variable name like POST_POST or GET_GET, meaning instead of the name James or Bond PHP returns either a "_GET" or a "_POST".
Since AbraCadaver asked full of solicitousness: "What in the world are you doing?"
here my solution and explanation:
Einacio: I coudn't create the names on the fly because the already arrive from a first function dynamically, so the actual variable name is not the true name.
And AbraCadaver pointed out that array_search() does not accept an array; unfortunately for sake of brevity I omitted that I pass on as a first argument not an array but another dynamic created variable from the root - I didn't want to make it too complicated, but basically it works like this:
function processUsers ($userName , $request2send ){
global ${$user.'_'.$request2send};
$url2send = "http...?request=".$request2send ;
...
$returnedValue = receivedDataArray ();//example elvis ([0] => Presley );
${$user.'_'.$request2send} = $returnedValue;
}
--- now Now I get the value of the function in the root ---
$firstValue = processUsers ("cuteAnimal" , "getName");
// returns: $cuteAnimal_getName = "Mouse"
and
$secondValue = processUsers ("actorRourke" , "getFirstName");
// returns: $actorRourke_getFirstName = "Mickey";
And now the bummer - a second function which needs the first one to be completed:
function combineValues ($firstValue , $secondValue ){
global ${$firstValue.'AND'.$secondValue};
${$firstValue.'_'.$secondValue} = $firstValue." ".$secondValue;
}
// returnes $actorRourke_getFirstNameANDcuteAnimal_getName = "Mickey Mouse";
Of course the second function is much more complicated and requires first to be completed,
but I hope you can understand now that it is not an array directly which I passed on but dynamic variable names which I could not just use as "firstValue" but I needed the name "actorRourke_getFirstName".
So AbraCadaver's suggestion to use $GLOBALS[..] did not work for me since it requires arrays.
However: Thanks for all your help and I hope I could now explain the issue to you.

Argument 1 for array_search() does not accept an array.
print_r($GLOBALS); will show the empty $_GET and $_POST arrays.
What in the world are you doing?
To go with Einacio:
function showArrayIntersection($ar1, $ar2) {
$GLOBALS[$ar1 . '_' . $ar2] = implode(array_intersect($GLOBALS[$ar1], $GLOBALS[$ar2]));
}
showArrayIntersection('James', 'Bond');
echo "Moneypenny : $James_Bond\n";
You could check to make sure they exist of course isset().

how about just using the names of the variables? it would also avoid value conflicts
function showArrayIntersection($ar1, $ar2) {
$dynamicName = $ar1 . '_' . $ar2;
global ${$dynamicName};
${$dynamicName} = implode(array_values(array_intersect($_GLOBALS[$ar1], $_GLOBALS[$ar2])));
}
$Bankers = [6,7,0,6,5,6,2]; // `[]` is equivalent to `array()` introduced in PHP 5.4
$Bond = [6,7,0,5,0];
$Politicians = [4,6,1,6,4,6,3];
$James = [0,1,0,3,7];
showArrayIntersection('James', 'Bond');
showArrayIntersection('Bankers', 'Politicians');
echo "Moneysystem: $Bankers_Politicians\n";
echo "Moneypenny : $James_Bond\n";

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