Control Structures in PHP

1
Control Structures in PHP

• Bryan Duggan

2
Control Structures if statements

• if (a gt b)
• echo "a is bigger than b"
• if (a gt b)
• print "a is bigger than b"
• b a
• if (a gt b)
• print "a is bigger than b"
• else print "a is NOT bigger than b"
• if (a gt b)
• print "a is bigger than b"
• elseif (a b)
• print "a is equal to b"
• else print "a is smaller than b

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Example usage

• Example
• lthtmlgt
• ltheadgtlttitlegtYour browserlt/titlegtlt/headgt
• ltbodygt
• lth1gtYour Browserlt/h1gt
• ltpgt
• lt?php
• if( strstr(HTTP_USER_AGENT,"MSIE") )
• echo "You are using Internet
  Explorer"
• ?gt
• to view this page.
• lt/pgt
• lt/bodygt
• lt/htmlgt
• strstr is a function which checks if its 2nd
  argument is a substring of its 1st

4
Control constructs -- while

• These are just like their counterparts in C
• i 1
• while ( i lt 10 )
• echo i
• i 0
• do print i while (igt0)

5
Control constructs -- for

• These are just like their counterparts in C
• for (i 1 i lt 10 i)
• print i

6
Control constructs -- foreach

• These are similar their counterparts in Perl
• foreach(array_expression as value)
• statement
• foreach(array_expression as key gt value)
• statement

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Jumping in and out of PHP mode

• We can can jump in and out of PHP mode even in
  the middle of a PHP block
• lt?php
• if(strstr(HTTP_USER_AGENT,"MSIE"))
• ?gt ltpgtYou are using Internet
  Explorerlt/pgt lt?php
• else ?gt ltpgtYou are not using Internet
  Explorerlt/pgt lt?php
• ?gt
• Instead of using an echo statement to print
  something, we jumped out of PHP mode.
• Note that the logical flow of the PHP remains
  intact
• Only one of the HTML blocks will be sent to the
  user.

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A FORM and its handler in one file

• lthtmlgt
• ltheadgt
• lttitlegtApplication Handlerlt/titlegt
• lt/headgt
• ltbodygt
• lt?php
• if (!_POSTsurname)
• ?gt ltform method"POST"
• action"http//student.cs.ucc.ie/cs4400/jabo
  wen/php/file012.php"gt
• ltpgtYour surname ltinput type"text"
  name"surname"gtlt/pgt
• ltpgtYour address ltinput type"text"
  name"address"gtlt/pgt
• ltbutton type"submit"gtPlease send me the
  brochure.lt/buttongt
• lt/formgt
• lt?php
• else echo "ltpgtThank you, surname.lt/pgt"
• echo "ltpgt We will write to you at
  address.lt/pgt" ?gt
• lt/bodygt
• lt/htmlgt

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Finding out about your PHP environment

• One of the many pre-defined PHP functions is
  phpinfo()
• lthtmlgt
• ltbodygt
• lth1gtYour PHP Environmentlt/h1gt
• lt?php phpinfo() ?gt
• lt/bodygt
• lt/htmlgt
• In what follows, notice that mySQL support is
  enabled

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Adding Comments to a PHP Script

• Comments are nonprinting lines placed in code
  such as
• The name of the script
• Your name and the date you created the program
• Notes to yourself
• Instructions to future programmers who might need
  to modify your work

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Adding Comments to a PHP Script (continued)

• Line comments hide a single line of code
• Add // or before the text
• Choose and stick with version
• Block comments hide multiple lines of code
• Add / to the first line of code
• And / after the last character in the code

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Example Comments

• lt?php
• /
• This line is part of the block comment.
• This line is also part of the block comment.
• /
• echo (lth1gtComments Examplelt/h1gt) // Line
  comments can follow
• code statements
• // This line comment takes up an entire line.
• This is another way of creating a line comment.
• / This is another way of creating
• a block comment. /
• ?gt