Using Numbers

Mar 9, 2017

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This chapter is from the book 

PHP for the Web: Visual QuickStart Guide, 5th Edition

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Review and Pursue

If you have any problems with the review questions or the pursue prompts, turn to the book’s supporting forum (www.LarryUllman.com/forums/).

Review

What are the four primary arithmetic operators?
Why will the following code not work:
```
print "The total is $$total";
```
What must be done instead?
Why must an HTML page that contains a form that’s being submitted to a PHP script be loaded through a URL?
What functions can be used to format numerical values? How do you format numbers to a specific number of decimals?
What is the importance of operator precedence?
What are the incremental and decremental operators?
What are the arithmetic assignment operators?

Pursue

Look up the PHP manual page for one of the new functions mentioned in this chapter. Use the links on that page to investigate a couple of other number-related functions that PHP has.
Create another HTML form for taking numeric values. Then create the PHP script that receives the form data, performs some calculations, formats the values, and prints the results.

Other Mathematical Functions

PHP has a number of built-in functions for manipulating mathematical data. This chapter introduced round(), number_format(), and mt_rand().

PHP has broken round() into two other functions. The first, ceil(), rounds every number to the next highest integer. The second, floor(), rounds every number to the next lowest integer.

Another function the calculator page could make good use of is abs(), which returns the absolute value of a number. In case you don’t remember your absolute values, the function works like this:

$number = abs(-23); // 23
$number = abs(23); // 23

In layman’s terms, the absolute value of a number is always a positive number.

Beyond these functions, PHP supports all the trigonometry, exponent, base conversion, and logarithm functions you’ll ever need. See the PHP manual for more information.

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