ITEC 325 2011spring ibarland

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ch04
Using Numbers
chapter 4

From PHP Visual Quickstart Guide by Larry Ullman
Based on notes by Jack Davis (jcdavis@radford.edu)

• Numeric Operators (functions invoked w/o parentheses): +, -, *, / (always floating-point division, not quotient).
• PHP supports assignment operators.
  +=, -=, *=, /=, ++, --.
  E.g. $total += 44; Note that unlike the numeric operators, the left-hand-side must of course be a variable (not any ol' numeric-expression), just like in other languages¹
• Precedence. Like other languages, PHP has a precedence order for operators. But to avoid problems with precedence in calculations, fully² parenthesize expressions (just like you should in other languages).
• Some numeric functions:
  • round(4.35) == 4 round(4.289,2) == 4.29 $num = 236.26985; round ($num) == 236
  • ceil rounds to the next higher integer: ceil(44.3) == returns 45.
    floor rounds to the next lower integer: floor(44.9) == 44.
    Note that floor differs from truncation on negative numbers: floor(-3.5) == -4.
• Formatting Numbers

  • number_format(428.4959,2) == '428.50' number_format(428,2) == '428.00' number_format(123456789) == '123,456,789'

    number_format can use two other optional arguments to indicate symbols for decimal points and break thousands
    can also use sprintf, printf to provide formats for output numbers
• Random Numbers
  

  echo rand(1,99); // random number in [1,99] (inclusive) echo rand(); // a random number in [0,getrandmax()]

• The php manual lists many more math functions that can be used; we've just reviewed some of the frequently used ones.
• Example: Form Calculation
• Example: Random numbers
• Variable Type Coercion in PHP

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