Because of PHP’s lax attitude toward type definitions, variables are sometimes automatically cast to best fit the circumstances in which they are referenced. Consider the following snippet:

$total = 5; // an integer
$count = "15"; // a string
$total += $count; // $total = 20 (an integer)

The outcome is the expected one; $total is assigned 20, converting the $count variable from a string to an integer in the process. Here’s another example demonstrating PHP’s type-juggling capabilities:

$total = "45 fire engines";
$incoming = 10;
$total = $incoming + $total; // $total = 55

The integer value at the beginning of the original $total string is used in the calculation. However, if it begins with anything other than a numerical representation, the value is 0. Consider another example:

$total = "1.0";
if ($total) echo "We're in positive territory!";

In this example, a string is converted to Boolean type in order to evaluate the if statement. Consider one last particularly interesting example. If a string used in a mathematical calculation includes ., e, or E (representing scientific notation), it will be evaluated as a float:

$val1 = "1.2e3"; // 1,200
$val2 = 2;
echo $val1 * $val2; // outputs 2400