# Thread: Multiply matching keys in two arrays

1. ## Multiply matching keys in two arrays

Oh ok. I do have a question though: Say I have two arrays where the first array contains the number of "tutoring sessions" and the second array contains the "lesson duration":

PHP Code:
``` Array ([0] => 2  [1] => 3 ) Array ([0] => 45  [1] => 90 )  ```
and what I want to do is multiply the matching keys between the two. For example, key of [0] is in both arrays and i want to multiply 2 * 45 and 3 * 90.

In addition do that I want to take those results and add them together to get total minutes (in this example, it is 90 + 270 = 360). From there I would take the result and say like "Total lesson minutes: 360"

2. PHP Code:
``` \$sessions = array(2, 3);\$duration = array(45, 90);\$total = 0;foreach(\$sessions as \$i => \$num) {  if (isset(\$duration[\$i]))    \$total += \$num * \$duration[\$i];}echo 'Total lesson minutes: ', \$total;  ```

3. PHP Code:
``` <?phpfunction multiply(\$a, \$b){  return \$a * \$b;}function stuff(\$arrayOne, \$arrayTwo){  \$computed = array();  for(\$index = 0; \$index < count(\$arrayOne); \$index++){    array_push(\$computed, multiply(\$arrayOne[\$index], \$arrayTwo[\$index]));  }  return array_sum(\$computed);}echo stuff(  array(100, 5),  array(5, 10)); #550?> ```
Off Topic:

Dammit ScallioXTX!

4. Thanks ScallioXTX! Your solution helped me out and now I know something to use in the future that I was stumped with before. This forum never disappoints with the quick and concise help.

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