Proofreading edits

code/arithmetic.php

@@ -5,10 +5,10 @@ $a = 1;
 $b = 2;
 
 // To add two values, use the plus symbol.
-$c = $a + $b;
+echo $a + $b;
 
 // To subtract, use the minus symbol.
-$c = $b - $a;
+echo $b - $a;
 
 // To multiply two values, use an asterisk.
 echo $a * $b;
@@ -18,8 +18,8 @@ echo $b / $a;
 
 // PHP uses the percent symbol for calculating the modulus of two numbers.
 // The modulus is calculated by dividing two numbers and returning the remainder of the result.
-// So, in this example, the value of $modulo will be 0.
-$modulo = 10 % 5;
+// In this example, the value of $mod will be 0.
+$mod = 10 % 5;
 
 // You can also use double asterisks to calculate a number to the power of another number.
 // The following statement will print 25.

code/variables.php

@@ -19,7 +19,7 @@ $var = 'I am a new variable';
 // An int is a number without a decimal place.
 // A float is a number with a decimal place.
 // A boolean can be two values: true or false.
-// Last, there is a string, a collection of characters.
+// Last, there is a string: a collection of characters.
 $int = 1;
 $float = 100.10;
 $bool = true;