如何轻松找到与动态字符串变量对应的变量总和？

Question

I'm completely stumped on how to accomplish my task programmatically.

I have a dynamically changing alpha string variable named $string. I have corresponding values set to each letter in the alphabet. I need to be able to automatically calculate the value of $total_string_length based on the letters within the $string variable.

$string = "jack"

$A_length = 1000;
$B_length = 500;
$C_length = 200;
$D_length = 1000;
$E_length = 1400;
$F_length = 100;
$G_length = 5000;
$H_length = 2000;
$I_length = 600;
$J_length = 8000;
$K_length = 8000;
etc...

$total_string_length = $J_length  + $A_length + $C_length + $K_length

How do I easily substitute the corresponding alpha letter variable values to find the $total_string_length ?

Any help is much appreciated.

Answer 1

PHP can use dynamic variable names.

$string = "jack";

$A_length = 1000;
$B_length = 500;
$C_length = 200;
$D_length = 1000;
$E_length = 1400;
$F_length = 100;
$G_length = 5000;
$H_length = 2000;
$I_length = 600;
$J_length = 8000;
$K_length = 8000;

$output = 0;
for($i = 0; $i < strlen($string); $i++) {
    $varName = strtoupper($string[$i]) . "_length";
    $output += $$varName; // notice the double `$` charaters
}

echo $output;

In the above code snippet, the value of the $varName variable is the name of the variable we want to get the number from. If $varName is A_length then $$varName is equivalent to $A_length.

However, it's better to store your number in an array instead of a list of separated variables.