How to parse a urlencoded query string into an array in PHP (without name changes)

Question

I know what you're thinking. "I can answer this question so quick! It's the parse_str function!" But I've got a little twist for you.

You see, PHP converts the names of all query data into valid PHP variable names. What? Even when they're not being stored as variables? Where is that documented? It isn't.

$payload = 'data.name=value&data.other=value2';
parse_str($payload, $values);
var_export($values);
// Outputs:  array('data_name' => 'value', 'data_other' => 'value2')
// Expected: array('data.name' => 'value', 'data.other' => 'value2')

How can I parse a query string without this happening?

Answer 1

You can avoid PHP's renaming of parameter names by parsing the query string yourself. Split the string on & and = characters, and then urldecode() each part:

<?php

  $payload = 'data.name=value&data.other=value2';

  $values = array();

  $nv_strings = explode ('&', $payload);
  foreach ($nv_strings as $s) {
    $nv = explode ('=', $s, 2);
    $name = urldecode ($nv[0]);
    $value = (isset ($nv[1]) ? urldecode ($nv[1]) : null);
    $values[$name] = $value;
  }

  print_r ($values);

//  Array
//  (
//      [data.name] => value
//      [data.other] => value2
//  )

---

If your query string contains duplicate keys, the above code will overwrite the previous keys. This also can be solved:

<?php

  $payload = 'key=val1&key=val2&key=val3';

  $values = array();

  $nv_strings = explode ('&', $payload);
  foreach ($nv_strings as $s) {
    $nv = explode ('=', $s, 2);
    $name = urldecode ($nv[0]);
    $value = (isset ($nv[1]) ? urldecode ($nv[1]) : null);
    $values[] = array ($name => $value);
  }

  print_r ($values);

//  Array
//  (
//      [0] => Array ([key] => val1)
//      [1] => Array ([key] => val2)
//      [2] => Array ([key] => val3)
//  )

---

You may want to consolidate the duplicate keys into subarrays:

<?php

  $payload = 'key1=val1&key1=val2&key2=val3';

  $values = array();

  $nv_strings = explode ('&', $payload);
  foreach ($nv_strings as $s) {
    $nv = explode ('=', $s, 2);
    $name = urldecode ($nv[0]);
    $value = (isset ($nv[1]) ? urldecode ($nv[1]) : null);
    if (isset ($values[$name])) {
      if (is_array ($values[$name])) {
        $values[$name][] = $value;
      } else {
        $values[$name] = array ($values[$name], $value);
      }
    } else {
      $values[$name] = $value;
    }
  }

  print_r ($values);

//  Array
//  (
//      [key1] => Array ([0] => val1
//                       [1] => val2)
//      [key2] => val3
//  )

---

You can simplify the code somewhat by always using subarrays:

<?php

  $payload = 'key1=val1&key1=val2&key2=val3';

  $values = array();

  $nv_strings = explode ('&', $payload);
  foreach ($nv_strings as $s) {
    $nv = explode ('=', $s, 2);
    $name = urldecode ($nv[0]);
    $value = (isset ($nv[1]) ? urldecode ($nv[1]) : null);
    if (isset ($values[$name])) {
      $values[$name][] = $value;
    } else {
      $values[$name] = array ($value);
    }
  }

  print_r ($values);

//  Array
//  (
//      [key1] => Array ([0] => val1
//                       [1] => val2)
//      [key2] => Array ([0] => val3)
//  )

Answer 2

It is documented completely in PHP Documentation for the function parse_str If the output does not work for your particular use case, then you must use another function, or create your own. The key here is that this function parses the string into variables.

parse_str — Parses the string into variables Parses str as if it were the query string passed via a URL and sets variables in the current scope.

To parse the string you provided, this would work:

$payload = 'data.name=value';
$map = array();
$vals = preg_split('/=/', $payload);
$i= 0;
while($i < count($vals)) {
  $map[$vals[$i]] = $vals[++$i];
  $i++;
}

var_dump($map);