Dynamic formation of variable name in PHP? - php

Question

The code below dynamically concatenates keys to an existing array $options_pool. So the final form should be: $options_pool[ $base_key ][ $first_key ][ $second_key ]... This is so I can dynamically assign a value to the elements of the array $options_pool which is multidimensional.
foreach( $this->post_vars as $name => $value ) {
//Look for $name key in array $options_pool if it exists.
//Use multi_array_key_exists() to handle the task
//It should return something like "fruit:mango:apple_mango"
//Then dynamically call $options_pool based on the data. Like so: $options_pool[ 'fruit' ][ 'mango' ][ 'apple_mango' ] = $value;
$match_key = multi_array_key_exists( $name, $options_pool );
$option_keys = explode( ':', $match_key );
$option_keys_length = count( $option_keys );
$option_name_array = array();
if( 0 < $option_keys_length ) {
for( $c = $option_keys_length; $c > 0; $c-- ) {
$sub_keys = '$options_pool';
for( $c_sub = 0; $c_sub < $c ; $c_sub++ ) {
$sub_keys .= '[ $option_keys[ '. $c_sub . ' ] ]';
}
$option_name_array[] = $sub_keys;
}
foreach( $option_name_array as $f_var_name ) {
//the following line should equal to: $options_pool[ 'fruit' ][ 'mango' ][ 'apple_mango' ] = $value;
$f_var_name = $value;
}
}
}
//The $options_pool array
$options_pool = array( 'car' => '', 'animals' => '', 'fruit' => array( 'mango' => array( 'apple_mango' => '' ));
I think the logic is correct except that this portion of the code:
foreach( $option_name_array as $f_var_name ) {
$f_var_name = $value; //particularly this line
}
doesn't work? I've tested printing the value of $f_var_name and the result is correct but it doesn't really call the array?

Answer 1

That is incorrect, you are right.
The variable name will always be $options_pool.
You can pass the keys as explode(':', $name) and later assign them.
By the way, your code at
foreach( $option_keys as $option_keys_value ) {
$option_key_names[] = $option_keys_value;
}
Do you realize that it just copies $option_keys as $option_key_names just as if you had written $option_key_names = $option_keys; (in this code) ?
Maybe with a stack you could do this iteratively but with recursion it is just more natural, as you see here
function getVariableToWrite(&$reference, $nested_opts, $write) {
if(empty($nested_ops)) // Base case
return $reference = write;
if(isset($reference[array_shift($nested_ops)]))
return getVariableToWrite($reference, $nested_ops, $write);
throw new Exception("The key does not exist..");
}
And then just
foreach( $this->post_vars as $name => $value ) {
// Your work over here until...
$match_key = "fruit:mango:apple_mango";
$option_keys = explode( ':', $match_key );
getVariableToWrite($options_pool, $option_keys, $value);
}
Will this do the work?

Answer 2

In your foreach, you need to pass the value by reference, so you can edit it.
foreach( $option_name_array as &$f_var_name ){
$f_var_name = $value;
}

Answer 3

Try this...
foreach( $option_name_array as $key => $f_var_name ) {
$option_name_array[$key] = $value; //particularly this line
}