: Edwin

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• ?? Edwin
• ?? kcchu6_at_cse.cuhk.edu.hkMSN
  ed_at_edwinchu.infoICQ 46374052???? 98340556
• ???? http//edwincheese.schtuff.com/interactive_w
  eb_programming

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• ???
• PHP ??(????)??????????

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Intro to PHP

• What is PHP?
• Language developed by Rasmus Lerdorf from the
  Apache Group
• Its primary use is for server-side scripting
• Ex To process HTML forms
• PHP scripts are typically embedded within html
  documents
• The server processes the html document, executing
  the PHP segments and substituting the output
  within the html document

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Intro to PHP

• The following .php file produces the html shown
• lthtmlgt
• ltheadgt
• lttitlegtFirst PHP Examplelt/titlegt
• lt/headgt
• ltbodygt
• lt?php echo "ltpgtlth1gtOutputlt/h1gt"
• echo "lth2gtOutputlt/h2gt"
• echo "lth3gtOutputlt/h3gtlt/pgt"
• ?gt
• ltscript language"PHP"gt
• echo "\nltbgtMore PHP Outputlt/bgtltbr /gt\n"
• lt/scriptgt
• lt/bodygt
• lt/htmlgt
• --------------------------------------------------
  --------------
• lthtmlgt
• ltheadgt
• lttitlegtFirst PHP Examplelt/titlegt

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Intro to PHP

• Simple (scalar) types
• boolean
• TRUE or FALSE
• integer
• Platform dependent size of one machine word
• 32 bits on most machines
• float
• Double precision
• We could call it a double, but since we don't
  declare variables (we will discuss shortly) float
  works

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Intro to PHP

• string
• We have single-quoted and double-quoted string
  literals
• Double quoted allows for more escape sequences
  and allows variables to be interpolated into the
  string
• What does that mean?
• Rather than outputting the name of the variable,
  we output its contents, even within a quote
• We'll see an example once we define variables
• Note that this is NOT done in Java
• Length can be arbitrary
• Grows as necessary

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Intro to PHP

• PHP variables
• All PHP variables begin with the
• Variable names can begin with an underscore
• Otherwise rules are similar to most other
  languages
• Variables are dynamically typed
• No type declarations
• Variables are BOUND or UNBOUND
• Unbound variables have the value NULL
• Type information is obtained from the current
  bound value

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Intro to PHP

• PHP programs have access to a large number of
  predefined variables
• These variables allow the script access to server
  information, form parameters, environment
  information, etc.
• Ex
• _SERVER is an array containing much information
  about the server
• _POST is an array containing variables passed to
  a script via HTTP POST
• _COOKIE is an array containing cookies
• See ex4.php

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Intro to PHP

• PHP Expressions and Operators
• Similar to those in C / Java / Perl
• Be careful with a few operators
• / in PHP is always floating point division
• To get integer division, we must cast to int
• x 15
• y 6
• echo (x/y), (int) (x/y), "ltBR /gt"
• Output is 2.5 2
• Inequality operators do not compare strings
• Will cast strings into numbers before comparing

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Intro to PHP

• To compare strings, use the C-like string
  comparison function, strcmp()
• Other string functions are listed on p. 482
• Even the operator has odd behavior in PHP when
  operands are mixed
• Ex Consider comparing a string and an int
• Any non-numeric PHP string value will equal 0
• Any numeric PHP string will equal the number it
  represents
• Ex Consider comparing a string and a boolean
• Regular PHP string value will equal true
• 0 string will equal false
• This behavior is consistent but confusing to the
  programmer and is probably best avoided

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Intro to PHP

• An additional equality operator and inequality
  operator are defined
• returns true only if the variables have the
  same value and are of the same type
• If casting occurred to compare, the result is
  false
• ! returns true if the operands differ in value
  or in type
• Precedence and associativity are similar to
  C/Java
• See Table 11-1 in the online PHP manual

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Intro to PHP

• PHP Control Structures
• Again, these are similar to those in C / Java
• if, while, do, for, switch are virtually
  identical to those in C and Java
• PHP allows for an alternative syntax to designate
  a block in the if, while, for and switch
  statements
• Open the block with rather than
• Close the block with endif, endwhile, endfor,
  endswitch
• Advantage to this syntax is readability
• Now instead of seeing a number of close braces,
  we see different keywords to close different
  types of control structures

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Intro to PHP

• A nice feature of PHP is that the "control"
  resulting from a control structure is maintained
  even when you exit back to html mode
• Thus, in lt?php you can branch / loop etc.
• You can then exit php ?gt and format in straight
  html
• PHP also has the foreach loop
• We will look at this when we discuss arrays
• See ex5.php

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Processing Forms with PHP

• Using PHP with forms fairly simple
• When forms are submitted the server executes the
  php script, returning the resulting html
• Remember that some of the file is unchanged,
  since it may not have an embedded php script
  within it
• Server can be set to that the form variables can
  be accessed directly by simply using the sign
• However, it is better to access the variables
  from the _POST array (or the _GET array)
• The form element name is the key into the array
• Discuss

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Processing Forms with PHP

• We can also use PHP to create forms
• However, it is really just HTML that we are using
• We can "interleave" the PHP and html to get the
  desired overall result
• So if you don't know it yet learn some HTML