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Implicit and Explicit Casting

PHP is a loosely typed language that allows you to declare a variable and its type simply by using it. It also automatically converts values from one type to another whenever required. This is called implicit casting.
However, there may be times when PHP’s implicit casting is not what you want. In Example 4-37, note that the imputs to the division are integers. By default, PHP converts the output to floating-point so it can give the most precise value – 4.66 recurring.
Example 4-37. This expression returns a floating-point number

But what if we had wanted $c to be an integer instead? There are various ways in which this could be achived. One way is to force the result of $a /$b to be an integer value using the integer cast type (int), like this:

$c = (int) ($a / $b);

This is called explicit casting. Note that in order to ensure that the value of the entire expression is cast to an integer, the expression is placed within parentheses. Otherwise, only the variable $a would have been cast to an integer – a pointless exercise, as the division by $ b would still have returned a floating-point number.
You can explicitly cast to the types shown in Table 4-6, but you can usually avoid having to use a cast by calling one of PHP’s built-in functions. For example, to obtain an integer value, you could use the intval (获取变量的整数值,转为整数) function. As with some othersections in this book, this one is mainly here to help you understand third-party code that you may encounter.
Table 4-6. PHP’s cast types

Cast type Description
(int) (integer) Cast to an integer by dropping the decimal portion
(bool) (boolean) Cast to a Boolean
(float) (double) (real) Cast to a floating-point number
(string) Cast to a string
(array) Cast to an array
(object) Cast to an object
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文章名称:《Implicit and Explicit Casting》

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