Dynamically create variables from $_POST fields on a form

Question

I'm having trouble creating variables from $_POST variables dynamically.

On a form, I have a table where people fill out driver information. The table has one row originally, but if more rows need to be added, the user presses a button, a new row is added, and the field names in the new row increment, i.e: driver1, driver2, driver3, driver4.

I'm trying to get this to match up with my PHP script:

$count=1; 

while($count<=100) {
  $driver . string($count) = $_POST['driver . string($count)'];
  $count++;
}

Normally I would create a new variable for each $_POST variable, but in the case of there being up to 100 rows, I'd like to handle this with a loop.

The error I'm receiving is:

Fatal error: Can't use function return value in write context in C:\Inetpub\vhosts\host\httpdocs\process.php on line 11

What's your goal here: $driver . string($count) = $_POST['driver . string($count)'];? You have an assignment = $_POST... in the middle of a concatenation. — Michael Berkowski
– Michael Berkowski, Commented Jun 9, 2014 at 16:01
Ohhh I get it. You're trying to build variable variables. Why not just keep them in an array? They are, after all, related. They are better organized inside a data structure. — Michael Berkowski
– Michael Berkowski, Commented Jun 9, 2014 at 16:04
@MichaelBerkowski - I foresee a large number of isset calls... — Mr. Llama
– Mr. Llama, Commented Jun 9, 2014 at 16:09

Andreas Storvik Strauman · Accepted Answer · 2018-09-19 09:59:19Z

2

Not reccomended to generate variables programatically. However it is possible:

${'driver'.$count}:

$count=1; 

while($count<=100) {
  ${'driver'.$count} = $_POST['driver' . $count];
  $count++;
}

More about dynamic variables here.

I would use arrays to accomplish this though:

$driver[$count]=$_POST['driver'.$count];

Then you can do

foreach ($driver as $count => $postValue){
    // $handling here
}

// OR to access a specific driver
$driver[$count];

edited Sep 19, 2018 at 9:59

answered Jun 9, 2014 at 16:01

Andreas Storvik Strauman

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1 Comment

Mr. Llama Over a year ago

I'm pretty sure OP meant $_POST['driver' . string($count)] unless they actually have post fields called driver . string(42).

Community · Accepted Answer · 2017-05-23 12:20:57Z

1

Try this

<?php

$count=1; 

while($count<=100) {
  ${'driver' . $count} = $_POST['driver' . $count];
  $count++;
}

?>

Since $count is a numeric value you don't need to do string cast.

I think this can help you to improve your code Count the number of times a specific input is present in an form

edited May 23, 2017 at 12:20

CommunityBot

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answered Jun 9, 2014 at 16:09

martinezjc

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Comments

ffflabs · Accepted Answer · 2014-06-09 16:04:17Z

0

you can use extract to map each $_POST key to a variable of the same name.

extract($_POST,EXTR_OVERWRITE,'prefix');

This will result in variables named $prefix_driver1, $prefix_driver2... and so on.

(use of prefix is optional, but if you don't use it, a malicious user can manipulate you script variables just by changing the form's input names)

answered Jun 9, 2014 at 16:04

ffflabs

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