PHP: Format variable by predetermined CSV order... but Why this code as function breaks?

Question

This code works perfectly... but why I got error using it as PHP function?

$name = '1 value';
$age  = '2 value';
$date = '3 value';

$string = "date, name, age"; //default CSV file Column order

Will get great results:

date, name, age

date|name|age
3 value|1 value|2 value|

By using this code:

echo $string.'<br/>'; 

echo implode("|", explode(", ", $string)).'<br/><br/>';

    $line='';
    foreach(explode(", ", $string) as $str)    {
            $line .= $$str.'|';
    }
    echo $line;

I code this function:

<?php
function toImplode($string)
{
    $line = '';
    foreach (explode(", ", $string) as $str) {
        $line .= $$str . '|';
    }
    return $line;
}

echo 'Variable to line formatted order is:<br/> ' . toImplode($string) . '<br/>';

But I got this error:

> Notice: Undefined variable: name in on line 22 
> Notice: Undefined variable: age in on line 22 
> Notice: Undefined variable: date in on line 22

I can't understand why.

Answer 1

You can use the global keyword with variable variables ($$):

Add the following line into the function body

global $$str; 

So the full code becomes:

<?php

$name = '1 value';
$age  = '2 value';
$date = '3 value';
$string = "date, name, age";

function toImplode($string) { $line=''; foreach(explode(", ", $string) as $str){ global $$str; $line .= $$str.'|';} return $line;} 

echo 'Variable to line formatted order is: '.toImplode($string).'<br/>';

Output:

Variable to line formatted order is: 3 value|1 value|2 value|<br/>

Try it online!