Powering Scripts with Functions

1
Powering Scripts with Functions

• David Lash
• Chapter 4
• Using and writing your own functions

2
Objectives

• Introduce this notion of a function
• Some basic numeric PHP functionsE.g., sqrt(),
  round(), is_numeric(), and rand().
• The print() function
• The date() function.
• See what we can do for ourselves

3
Using Some Basic PHP Functions

• PHP has a bunch of built-in functions.
• They do things automatically for you
• For example,
• print (Hello World)
• We will look at other functions that do things
  for you

Creates output with its one argument (or input
variable).
Name of function
4
The sqrt() Function Just to warm-up

• sqrt() - input a single numerical argument and
  returns its square root.
• For example, the following
• xsqrt(25)
• ysqrt(24)
• print "xx yy"
• Will output
• x5 y4.898979485566
• y144
• num sqrt(y)

Function name
Argument or parameter to function
Returned value
5
The round() Function

• round() - rounds number to nearest integer
• For example, the following
• xround(-5.456)
• yround(3.7342)
• print "xx yy"
• Will output x-5 y4

6
True/false Return values

• So far functions have either returned nothing
  (e.g., print() ) or a number (e.g., round() )
• Functions can also return a true or false value.
• True is sometimes thought of 1 and false of 0
• These are called boolean returned
• Why would you do this? .
• Makes testing something easy
• if ( got_a_number() ) do stuff
• Lets look at a true/false function .

This is just an example it is not a valid
statement
7
The is_numeric() Function

• is_numeric() determines if a variable is a valid
  number or a numeric string.
• It returns true or false.
• Consider the following example...
• if (is_numeric(input))
• print "Got Valid Numberinput"
• else
• print "Not Valid Numberinput"
• If input was 6 then would Got Valid Number6
• If input was Happy then would output Not
  Valid NumberHappy

Could use to test if input was string or numeric
8
Remember this Consider average example

• lthtmlgt
• ltheadgt
• lttitlegtSurvey Formlt/titlegt
• lt/headgt
• ltbodygt
• lth1gtClass Surveylt/h1gt
• ltFORM METHOD"POST" ACTION"newaverage.php"gt
• ltbrgtPick A Number ltBRgt ltinput typetext
  namenum1gt
• ltbrgtPick A Number 2 ltBRgtltinput typetext
  namenum2gt
• ltbrgtPick A Number 3 ltBRgtltinput typetext
  namenum3gt
• ltbrgtltinput type"submit" value"Submit"gt
• ltinput type"reset" value"Erase"gt
• lt/formgt
• lt/BODYgt
• lt/HTMLgt

9
PHP Code

• lthtmlgt ltheadgt lttitlegt Guess the Dice lt/titlegt
• ltbodygt
• ltFont size5 colorblackgt Your Averages
  Arelt/fontgt
• ltform action"guessdice2.php" methodpostgt
• lt?php
• num1 _POSTnum1
• num2 _POSTnum2
• num3 _POSTnum3
• if ( !is_numeric(_POSTnum1)
  !is_numeric(_POSTnum2) !is_numeric(_POSTn
  um3) )
• print "Error please fill in numericaly
  values for all three inputs"
• print "num1num1 num2num2 num3num3"
• exit
• aver (num1 num2 num3 ) / 3
• print "ltfont size4 colorbluegt"
• print "num1 num1 "

http//condor.depaul.edu/dlash/extra/Webpage/exam
ples/newaverage.html
10
The rand() Function can be fun

• Use rand() to generate a random number.
• You can use random numbers to simulate a dice
  roll or a coin toss or to randomly select an
  advertisement banner to display.
• rand() gen a number from 1 to max number.
• E.g.,
• num rand()
• print numnum
• Might output
• num 12

11
The rand() Function - Part II

• Use the rand() to generate a number 1-6
• numb rand()
• rnumb (numb 6) 1
• print "Your random dice toss is rnumb"
• The random number generated in this case can be a
  1, 2, 3, 4, 5, or 6.

Think a second Asks for remainder of numb /
6 which is always 0,1,2,3,4, or 5 so you add 1 to
force it to be 1,2,3,4,5, or 6
12
A Full Example ...

• Consider the following application
• Uses an HTML form to ask the end-user to guess
  the results of dice roll
• ltinput type"radio" nameguess" value1"gt 1
• ltinput type"radio" nameguess" value2"gt 2
• ltinput type"radio" nameguess" value3"gt 3
• ltinput type"radio" nameguess" value4"gt 4
• ltinput type"radio" nameguess" value5"gt 5
• ltinput type"radio" nameguess" value5"gt 6
• http//condor.depaul.edu/dlash/extra/Webpage/exam
  ples/guessdice.php

13
Consider the following ...

• ltheadgt lttitlegt Guess the Dice lt/titlegt
• ltbodygt
• lt?php
• guess _POST"guess"
• if ( guess gt 1 guess lt6 )
• numb rand() 6 1
• print "numbnumb ltbrgt"
• dice"dicenumb.gif"
• print "The Random Dice Generated Is
  ..."
• print "ltimg srcdicegt"
• print " ltbrgt Your Dicedice ltbrgt"
• if ( guess numb )
• print "ltbrgtltfont size4
  colorbluegt You got it right "
• print "ltbrgt ltfont size4
  colorbluegt Your Guess is guess "
• else
• print "ltbrgt ltfont size4
  colorredgt You got it WRONG ? "
• print "ltbrgtltfont size4
  colorredgt Your Guess is guess "
• else

Generate random number 1-6
Set which image to display
Display either dice1.gif, dice2,gif,
dice3.gif, dice4.gif, dice5.gif, or dice6.gif
Check to see if got it right or wrong
14
Objectives

• To learn to use several PHP functions useful for
  Web application development
• Some basic numeric PHP functionsE.g., sqrt(),
  round(), is_numeric(), and rand().
• The print() function
• The date() function.
• To learn to write and use your own functions

15
More information on the print() Function

• You dont need to use parenthesis with print()
• Double quotes means output the value of any
  variable
• x 10
• print ("Mom, please send x dollars")
• Single quotes means output the actual variable
  name
• x 10
• print ('Mom, please send x dollars')
• To output a single variables value or
  expression, omit the quotation marks.
• x5
• print x3

Double quotes
Single quotes
16
Generating HTMLTags with print()

• Using single or double quotation statements can
  be useful when generating HTML tags
• print 'ltfont color"blue"gt'
• This above is easier to understand and actually
  runs slightly faster than using all double
  quotation marks and the backslash (\) character
• print "ltfont color\"blue\"gt"

using \ allows to be output
17
Objectives

• To learn to use several PHP functions useful for
  Web application development
• Some basic numeric PHP functionsE.g., sqrt(),
  round(), is_numeric(), and rand().
• The print() function
• The date() function.
• To learn to write and use your own functions

18
The date() Function

• The date() function is a useful function for
  determining the current date and time
• The format string defines the format of the
  date() functions output
• day date('d')
• print "dayday"
• If executed on December 27, 2001, then it would
  output day27.

Request date() to return the numerical day of the
month.
19
Selected character formats for date()
20
More About date()

• You can combine multiple character formats return
  more than one format from the date()
• For example,
• today date( 'l, F d, Y')
• print "Todaytoday"
• On MQY 11, 2004, would output
• TodayTuesday, May 11, 2004.

21
A Full Example ...

• Consider the following Web application that uses
  date() to determine the current date and the
  number of days remaining in a stores sale event.
• Sale runs from 12/1 until 1/10/02

22
Receiving Code

• 1. lthtmlgt ltheadgtlttitlegt Our Shop lt/titlegt lt/headgt
• 2. ltbodygt ltfont size4 color"blue"gt
• 3. lt?php
• 4. today date( 'l, F d, Y')
• 5. print "Welcome on today to our huge blowout
  sale! lt/fontgt"
• 6. month date('m')
• 7. year date('Y')
• 8. dayofyear date('z')
• 9. if (month 12 year 2001)
• 10. daysleft (365 - dayofyear 10)
• 11. print "ltbrgt There are daysleft sales days
  left"
• 12. elseif (month 01 year 2002)
• 13. if (dayofyear lt 10)
• 14. daysleft (10 - dayofyear)
• 15. print "ltbrgt There are daysleft sales
  days left"
• 16. else
• 19. print "ltbrgtSorry, our sale is over."
• 20.
• 21. else

Get a date in format day of week, month, day and
year
Get month number 1-12, , 4 digit year and day
of year
Check if its Dec 2001. Then figure out days left
in year and add 10.
If if 1/2002 already, how many days left before
1/10?
Otherwise sale is ove.
23
The Output ...

• The previous code can be executed at
  http//webwizard.aw.com/phppgm/C3/date.php

24
Create your own functions ...

• Write your own function to
• group a set of statements, set them aside, and
  turn them into mini-scripts within a larger
  script.
• The advantages are
• Scripts that are easier to understand and change.
• Reusable script sections.
• Smaller program size

25
Writing Your Own Functions

• Use the following general format
• function function_name()
• set of statements

Include parentheses at the end of the function
name
Use the keyword function here
The function runs these statements when called
Enclose in curly brackets.
26
For example

• Consider the following
• function OutputTableRow()
• print 'lttrgtlttdgtOnelt/tdgtlttdgtTwolt/tdgtlt/trgt'
• You can run the function by including
• OutputTableRow()

27
As a full example

• 1. lthtmlgt
• 2. ltheadgtlttitlegt Simple Table Function lt/titlegt
  lt/headgt ltbodygt
• 3. ltfont color"blue" size"4"gt Here Is a Simple
  Table lttable border1gt
• 4. lt?php
• 5. function OutputTableRow()
• 6. print 'lttrgtlttdgtOnelt/tdgtlttdgtTwolt/tdgtlt/tr
  gt'
• 7.
• 8. OutputTableRow()
• 9. OutputTableRow()
• 10. OutputTableRow()
• 11. ?gt
• 12. lt/tablegtlt/bodygtlt/htmlgt

OutputTableRow() function definition.
Three consecutive calls to the OutputTableRow()
function
28
Would have the following output
29
TIP Use Comments at the Start of a Function

• It is good practice to place comments at the
  start of a function
• For example,
• function OutputTableRow()
• // Simple function that outputs 2 table cells
• print 'lttrgtlttdgtOnelt/tdgtlttdgtTwolt/tdgtlt/trgt'

30
Passing Arguments to Functions

• Input variables to functions are called arguments
  to the function
• For example, the following sends 2 arguments
• OutputTableRow("A First Cell", "A Second Cell")
• Within function definition can access values
• function OutputTableRow(col1, col2)
• print "lttrgtlttdgtcol1lt/tdgtlttdgtcol2lt/tdgtlt/trgt"
  

31
Consider the following code

• 1. lthtmlgt
• 2. ltheadgtlttitlegt Simple Table Function lt/titlegt
  lt/headgt ltbodygt
• 3. ltfont color"blue" size4gt Revised Simple
  Table lttable border1gt
• 4. lt?php
• 5. function OutputTableRow( col1, col2 )
• 6. print "lttrgtlttdgtcol1lt/tdgtlttdgtcol2lt/tdgtlt
  /trgt"
• 7.
• OutputTableRow( Row 1 Col 1 , Row 1 Col 2 )
• OutputTableRow( Row 2 Col 1 , Row 2 Col 2 )
• OutputTableRow( Row 3 Col 1 , Row 3 Col 2 )
• OutputTableRow( Row 4 Col 1 , Row 4 Col 2 )
• 12. ?gt
• 13. lt/tablegtlt/bodygtlt/htmlgt

OutputTableRow() Function definition.
Four calls to OuputTableRow()
32
Returning Values

• Your functions can return data to the calling
  script.
• For example, your functions can return the
  results of a computation.
• You can use the PHP return statement to return a
  value to the calling script statement
• return result

• This variables value will be returned to the
  calling script.

33
Example function

• 1. function Simple_calc( num1, num2 )
• 2. // PURPOSE returns largest of 2 numbers
• 3. // ARGUMENTS num1 -- 1st number, num2 --
  2nd number
• 4. if (num1 gt num2)
• 5. return(num1)
• 6. else
• 7. return(num2)
• 8.
• 9.
• What is output if called as follows
• largest Simple_calc(15, -22)

Return num1 when it is the larger value.
Return num2 when it is the larger value.
34
Consider an application that
Main form element Starting Value ltinput
type"text" size"15 maxlength"20"
name"start"gt Ending Value ltinput type"text"
size"15 maxlength"20" name"end"gt
35
A Full Example ...

• Consider a script that calculates the percentage
  change from starting to an ending value
• Uses the following front-end form
• Starting Value ltinput type"text" size"15
  
• maxlength"20" name"start"gt
• Ending Value ltinput type"text" size"15
• maxlength"20" name"end"gt

http//webwizard.awl.com/phppgm/C4/driveperc.html
36
The Source Code

• 1. lthtmlgt
• 2. ltheadgtlttitlegt Your Percentage Calculation
  lt/titlegtlt/headgtltbodygt
• 3. ltfont color"blue" size4gt Percentage
  Calculator lt/fontgt
• 4. lt?php
• 5. function Calc_perc(buy, sell)
• 6. per ((sell - buy) / buy) 100
• 7. return(per)
• 8.
• 9. start _POSTstart end
  _POSTend
• 10. print "ltbrgtYour starting value was start."
• 11. print "ltbrgtYour ending value was end."
• 12. if (is_numeric(start) is_numeric(end) )
  
• 13. if (start ! 0)
• 14. per Calc_perc(start, end)
• 15. print "ltbrgt Your percentage change
  was per ."
• 16. else print "ltbrgt Error! Starting
  values cannot be zero "
• 17. else
• 18. print "ltbrgt Error! You must have valid
  numbers for start and end "
• 19.

Calculate the percentage change from the
starting value to the ending value.
The call to Calc_perc() returns the
percentage change into per.
37
Using External Script Files

• Sometime you will want to use scripts from
  external files.
• Reuse code from 1 situation to another
• Create header and footer sections for code
• PHP supports 2 related functions
• require ("header.php")
• include ("trailer.php")
• Both search for the file named within the double
  quotation marks and insert its PHP, HTML, or
  JavaScript code into the current file.

The require() function produces a fatal error if
it cant insert the specified file.
The include() function produces a warning if it
cant insert the specified file.
38
Consider the following example
The script will output these lines when the file
is included.

• 1. ltfont size4 color"blue"gt
• 2. Welcome to Harrys Hardware Heaven!
• 3. lt/fontgtltbrgt We sell it all for you!ltbrgt
• 4. lt?php
• 5. time date('Hi')
• 6. function Calc_perc(buy, sell)
• 7. per ((sell - buy ) / buy) 100
• 8. return(per)
• 9.
• 10. ?gt

The value of time will be set when the file is
included.
This function will be available for use when the
file is included.
39
header.php

• If the previous script is placed into a file
  called header.php
• 1. lthtmlgtltheadgtlttitlegt Hardware Heaven
  lt/titlegtlt/headgt ltbodygt
• 2. lt?php
• 3. include("header.php")
• 4. buy 2.50
• 5. sell 10.00
• 6. print "ltbrgtIt is time."
• 7. print "We have hammers on special for
  \sell!"
• 8. markup Calc_perc(buy, sell)
• 9. print "ltbrgtOur markup is only markup!!"
• 10. ?gt
• 11. lt/bodygtlt/htmlgt

Include the file header.php
Calc_perc() is defined in header.php
40
Would output the following ...
41
More Typical Use of External Code Files

• More typically might use one or more files with
  only functions and other files that contain HTML
• For example, might use the following as
  footer.php.
• lthrgt
• Hardware Harry's is located in beautiful downtown
  Hardwareville.
• ltbrgtWe are open every day from 9 A.M. to
  midnight, 365 days a year.
• ltbrgtCall 476-123-4325. Just ask for Harry.
• lt/bodygtlt/htmlgt
• Can include using
• lt?php include("footer.php") ?gt

42
Even More Practical Example

• Check out the following link http//condor.depaul.
  edu/dlash/website/Indellible_Technologies.php
• Original found at perl-pgm.com
• Could hard code header in each file that needs it
  or
• Separate the header info into a different file
  (Say header.php.)
• Include it everywhere needed.
• E.g., ltinclude header.phpgt
• lthtmlgt
• ltheadgt
• lttitlegtIndellible Technologieslt/titlegt
• lt/headgt
• ltbody text"000000" bgcolor"ffffff"
  link"000099" vlink"990099"
• alink"000099"gt
• lt?php include "header.php" ?gt

43
Here is contents of header.php

• lttable cellpadding"0" cellspacing"0" border"0"
  width"100"gt
• lttbodygt
• lttrgt
• lttd valign"top"gt ltimg
  src"INdelliblecolor3.gif" alt"" width"792"
• height"102"gt
• ltbrgt
• lt/tdgt
• lt/trgt
  
• lt/tbodygt
• lt/tablegt
• lttable cellpadding"0" cellspacing"0" border"0"
  width"792"gt
• lttbodygt
• lttrgt
• lttd valign"bottom"
  bgcolor"33ffff" align"center"gtlta
• href"requestinfo.html"gt
  Request Informationlt/agt lta
• href"preregister.html"gt
  Pre-registerlt/agt
• lta href"schedule.html
  "gtCourseCataloglt/agt
• nbsplta
  href"comments.html"gtTestimonialslt/agtltbrgt
• lt/tdgt

44
Summary

• To learn to use several PHP functions useful for
  Web application development
• Some basic numeric PHP functionsE.g., abs(),
  sqrt(), round(), is_numeric(), and rand().
• The print() function
• The date() function.
• To learn to write and use your own functions
• Writing own functions
• returning values
• Passing arguments

45
Here is the receiving code ...

• ltlthtmlgt ltheadgt lttitlegt Receiving Script lt/titlegt
  ltbodygt
• lt?php
• passwd _POST"pass"
• fname _POST"fname"
• if (passwd "password" )
• print "Thank you fname welcome
  ltbrgt"
• print "Here is my site's
  content"
• else
• print "Hit the road jack you
  entered passwordpasswdltbrgt"
• print "Contact someone to get the
  passwd"
• ?gt
• lt/bodygt lt/htmlgt

46
Summary

• Looked at using conditional statements
• if statement
• elsif statement
• else statement
• conditional statements have different format
• if ( x lt 100 )
• x y 1
• z y 2
• Can do multiple tests at once
• if ( x lt 100 name george )
• x y 1
• z y 2
• Can test if variable(s) set from form
• if ( !_POSTvar1 !_POSTvar1 )