Using arrays with strings with a while loop - php

Question

I am writing some code to create fields automatically, which will save me a load of time. I have got most of my code working, but I have came across one error with the code, which is preventing me from achieving my final goal.
The code is as follows:
while ($i <= $numFields) {
$type = "\$field{$i}_Data['type']";
$name = "\$field{$i}_Data['name']";
$placeholder = "\$field{$i}_Data['placeholder']";
$value = "\$field{$i}_Data['value']";
echo '<input type="'.$type.'" name="'.$name.'" placeholder="'.$placeholder.'" value="'.$value.'">';
$i++;
}
The $numFields variable is defined at the top of my script, and I have worked out that it is something to do with how I am setting the variables $type, $name etc.
The end result is to create inputs depending on properties set in variables at the top of the script, The only issue I am having is with the settings of the variables, as said above.
If any extra code/information is needed, feel free to ask.
Thank you.
NOTE - There is no physical PHP error, it's purely an error with this:
"\$field{$i}_Data['value']";

Answer 1

There are a few ways we could write this one out, but they are all extensions of variable expansion and/or variable-variables.
Basically, we just need to put the variable name in a string and then use that string as the variable (much like you're currently doing with $i inside the string):
$type = ${"field{$i}_Data"}['type'];
$name = ${"field{$i}_Data"}['name'];
// ...
However, if you don't mind an extra variable, this can be written more cleanly by saving it like so:
$data = ${"field{$i}_Data"};
$type = $data['type'];
$name = $data['name'];
// ...