Warning: array_push() expects parameter 1 to be array, string given

Question

I am getting Warning: array_push() expects parameter 1 to be array, string given in ... for array_push() on this piece of code. The warning occurs in the first push, how do I fix this?

$url = $_SERVER['QUERY_STRING'];

$chunk = explode("&",$url);
array_pop($chunk);

foreach($chunk as $key => $value)
{
    $pieces = explode("=",$value);
    if($pieces)
    {
        $val = $pieces[0];
        if(isset($$val))
        {
            array_push($$val,$pieces[1]);
        }else{
            $$val = array();
            array_push($$val,$pieces[1]);
        }
    }
}

Note: I am not using $_GET because my querystring can contain multiple parameters with the same name like this

?q=1&q=2&q=3&q=4

Answer 1

You don't need to explode and push/pop the query string. Just use the $_GET superglobal.

http://php.net/manual/en/reserved.variables.get.php

Edit: $_GET is an array, you can loop over it in the same way as any other array. If you need to get all of them separately then you can do this:

foreach ($_GET as $key => $value) {
    // whatever
}

Edit2: OK, I still think that whatever you are doing with those params is the wrong way to do it but if you need a function then you can try something like this:

function extractVars($url)
{
    $query = explode('?', $url);

    $extract = array();

    if (!isset($query[1])) {
        return $extract;
    }

    $params = explode('&', $query[1]);
    foreach($params as $param) {
        if (strpos($param, '=') !== false) {
            list($key, $value) = explode('=', $param);
            $extract[$key][] = $value;
        }
    }

    return $extract;
}

$string = 'url?a=1&a=2&a=3&b=1&b=2&b=3';
print_r(extractVars($string));

Which gives an output like this:

Array
(
  [a] => Array
  (
    [0] => 1
    [1] => 2
    [2] => 3
  )

  [b] => Array
  (
    [0] => 1
    [1] => 2
    [2] => 3
  )
)

Answer 2

This piece of code will only work if $$val is already an array. If it is not it will generate that error.

array_push($$val,$pieces[1]);

So try this :-

foreach($chunk as $key => $value)
{
    $pieces = explode("=",$value);
    if($pieces)
    {
        $val = $pieces[0];
        if( isset($$val) && is_array($$val) ) {
            array_push($$val,$pieces[1]);
        } else {
            $$val = array();
            array_push($$val,$pieces[1]);
        }
    }
}

Of course it would be easier to use the $_GET array which PHP prepares automatically for you

Additional thought after your comment

Could the reason for this warning be that you are using an old version of PHP and have the parameter register_globals = on.

So assuming a url of www.xx.com?q=1&q=2&q=3

This would mean that PHP had already created a $q variable for you. So the first pass through your code would find all the variables in the query string already exists as strings i.e. PHP will have already created the variables like this invisibly to you.

$q = '1';
$q = '2';
$q = '3';

So the first time your code attempts the array_push($$val,$pieces[1]); $$val which equates to $q but $q is already a scalar string variable, hence your error message.

You can check if this is the case by adding

print_r($GLOBALS);

just before the section of your script you posted. Then check the url against variables that already exist.

Another thought

The only way to explain this warning is that one or more of the variables you are trying to create in this code snippet already exists, for whatever reason.

Its quite possible that this code worked originally without the warning, but since then the code was amended and someone created one or more or there variables for some temporary purpose earlier on in the code.

As your querystring parameters equate to variables like

cid, val, np, wgt, w, l, h

Its quite possible someone used $w or $l or $h especially for some temporary purpose within a loop to hold a value. Its common practice to use single letter variables names to denote that the variable is only used within the few lines that you can see on a screen. But uncommon for people to destroy them once they are no longer required.

Anyway its worth having a look to see if one or more of these variable have been created prior to your code snippet.

Add a

print_r($GLOBALS) 

just before your code snippet and see if any of these variables already exist.

Answer 3

Given that the url is something like www....php?a=b&c=d&e=f, you explode it so several elements a=b, c=d, e=f. You drop the a&b, and continue with c=d and e=f. You then pickup the c=d, explode it into the values c and d. Therfore unlikely that c is an array, which is proven by the error message.

Try to look at the content by adding print_r($val) and print_r($$val). It should give you an overview of what is actually evaluated, and work from there. I think you will find out that the variable variable doesn't work as expected either.

Answer 4

OK guys I sorted it out by following your advice of getting rid of the loop code and replacing it with proper code.

It is now working perfectly and it was a simple solution.

$h   = $_GET["h"];
$w   = $_GET["w"];
$l   = $_GET["l"];
$wgt = $_GET["wgt"];
$np  = $_GET["np"];
$cid = $_GET["cid"];

if (!is_array($h))   $h   = [$h];
if (!is_array($w))   $w   = [$w];
if (!is_array($l))   $l   = [$l];
if (!is_array($wgt)) $wgt = [$wgt];

The first part gets the parameters into variables, one by one, the second part converts them into an array when it is a string.

Thanks for your help and advice. :)

Answer 5

Just remove the one dollar($) in the $$val.