Cannot unpack array with string keys
PhpArraysArgument UnpackingPhp Problem Overview
The error message is:
> FATAL ERROR Uncaught Error: Cannot unpack array with string keys
I know I can simply run the method fetch()
twice and pass the ['q']
and ['bind']
, but I am trying to get to grips with using the new ...
to unpack values. I want to pass the values like so:
(string) SQL, (Array) Bind Values
But I think it tries to unpack the bind values array as well as the response array from the fetch()
method. Is it possible to unpack this array?
It looks something like this:
array(2) {
["q"] => string(7) "example"
["bind"] => array(1) {
["example"] => string(3) "one"
}
}
This is the whole code, in case you need to see how it all fits together:
class ModelController {
public static function execute($sql, $vals) {
var_dump($vals);
}
}
class ModelContainer {
private $queries = [];
public function add_model(Model $model, $name) {
$this->queries[$name] = $model;
return $this;
}
public function exec_all() {
foreach($this->queries as $q) {
ModelController::execute(...$q->fetch());
}
}
public function exec($name) {
}
}
class Model {
private $sql;
private $vals = [];
public function set_q($statement) {
$this->sql = $statement;
return $this;
}
public function bind($vals = []) {
$this->vals = $vals;
return $this;
}
public function fetch() {
return ['q' => (string)$this->sql,
'bind' => $this->vals ];
}
}
$m = new ModelContainer();
$m->add_model((new Model)->set_q('example SQL content here')->bind(['example' => 'example value here']), 'one');
$m->exec_all();
Php Solutions
Solution 1 - Php
The problem is that the splat operator (array unpacking operator or ...
) does not work with associative arrays. Example:
$array = [1, 2, 3];
$assoc = ["one" => 1, "two" => 2, "three" => 3];
var_dump(...$array); //Works
var_dump(...$assoc); //Doesn't work
You need to force an array to be numerically indexed in order to unpack it. You do this using array_values:
$values = array_values($q->fetch());
ModelController::execute(...$values);
Array values will ensure all values have a sequential numeric key.
Update
Starting PHP 8 there will be support for named arguments which will make both cases work. An example is documented in the proposed RFC for named arguments which says the following code should work starting PHP 8
$params = ['start_index' => 0, 'num' => 100, 'value' => 50];
array_fill(...$params);
Solution 2 - Php
Update PHP 8.1
Since PHP 8.1, unpacking arrays also works with string-key arrays, so the error FATAL ERROR Uncaught Error: Cannot unpack array with string keys will not be applicable anymore.
Example:
$array1 = ["a" => 1];
$array2 = ["a" => 2];
$array = ["a" => 0, ...$array1, ...$array2];
var_dump($array); // ["a" => 2]
Solution 3 - Php
If you got this error when you tried to unpack an associative array into another array then you can use array_merge
instead:
<?php
$inner = ["b" => "i", "c" => "i"];
$outer = ["a" => "o", "c" => "o"];
var_dump(array_merge($outer, $inner));
var_dump(array_merge($inner, $outer));
will produce
array(3) {
["a"]=>
string(1) "o"
["c"]=>
string(1) "i"
["b"]=>
string(1) "i"
}
array(3) {
["b"]=>
string(1) "i"
["c"]=>
string(1) "o"
["a"]=>
string(1) "o"
}