Passing javascript array via POST to PHP does not working

Question

I need to pass a javascript array, via POST, to a PHP file.

I've tried to semplify my original business trying to explain my troubles ...

This is my first PHP file, in which I declare a javascript array and I set each element to 1 value (not a great business I know, but it doesn't matter, it's only to explain ....)

<?php

  echo '<form action="testPhp-2.php"  method="POST" target="testPhp-2">';

  echo '<script type="text/javascript">';

  echo 'var arr_selections = [];';
  echo 'for(i=0; i < 10; i++)';
  echo ' {';
  echo '  arr_selections[i] = 1';
  echo ' }';

  echo 'arr_selections_json = JSON.stringify(arr_selections);';
  echo 'alert (arr_selections[2]);';

  echo 'document.write("<br/>");';
  echo ' ';

  //        echo 'document.write("<input type="hidden" />");';
  echo 'document.write("<input type=\"hidden\" name=\"arr_selections_json\" value=\"arr_selections_json\" />");';
  echo ' ';

  echo '</script>';

  echo '    <input type="submit" value="Controlla">';
  echo '   </form>';


?>

.... and here you are the code of testPhp-2 file ...

<?php

  if(isset($_POST['arr_selections_json']))
   {
    echo "OK, array exist !! ";
    echo '</br>';
    echo '</br>';
    $arr_selections = json_decode($_POST['arr_selections_json'], true);
    echo $arr_selections[0];
   }
  else {
   echo "NO; array does not exist !! ";
   echo '</br>';
   echo '</br>';
  }

?>

Now, if you try to execute the code you'll see the OK, array exist !! message but no array value is printed about the echo $arr_selections[0]; line of code in testPhp-2.php file.

Any suggestion will be appreciated! Thank you in advance!

Cesare

You're passing the literal string arr_selections_json to the input field. That's all. — Charlotte Dunois
– Charlotte Dunois, Commented Aug 9, 2016 at 16:47
You should checkout the HEREDOC syntax, would be much less painful of an experience to write Javascript in PHP: php.net/manual/en/… — Rob M.
– Rob M., Commented Aug 9, 2016 at 16:48
@Charlotte Dunois .. do you mean that the problem is in this line of code in testPhp-1.php file? echo 'document.write("<input type=\"hidden\" name=\"arr_selections_json\" value=\"arr_selections_json\" />");'; How may I fix it? Thank you! — Cesare
– Cesare, Commented Aug 9, 2016 at 16:55

BeetleJuice · Accepted Answer · 2016-08-09 16:57:18Z

2

Problem is that you're setting the value of the input to the litteral string "arr_selections_json" instead of to the contents of that variable.

Change

echo 'document.write("... value=\"arr_selections_json\" />");';

To

echo 'document.write("... value=\""+arr_selections_json+"\" />");';

answered Aug 9, 2016 at 16:57

BeetleJuice

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1 Comment

Cesare Over a year ago

GREAT! It's working now .. this is out of my knowledge. Thanks a lot!

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