PHP : Hypertext Preprocessor

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PHP Hypertext Preprocessor
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What is PHP for?

• Unlike JavaScript which is a client-side script
  language, PHP is a server side script
• PHP is processed on the server, therefore you can
  not use the View/Source menu command to view
  someone else's PHP code. Finally someone is
  protecting my code. ?
• PHP programs/scripts perform several basic
  operations
• Obtain data from a user
• Perform computations
• Access and manipulate data stored in files and
  databases
• Display data so that a user can view it.

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My first PHP script

• Inside the regular html file
• You include the following tag
• lt?php
• // code here
• ?gt
• Make sure you save it as .php

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My first PHP script pex1.php

• lt?php
• echo 'Hello World'
• echo 'ltbr /gt lth1gt Hello Worldlt/h1gt'
• echo 'ltemgt Hello World lt/emgt '
• ?gt
• ! Before you upload to your server, make sure you
  make a directory call php so we know where to
  look for your code.

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PHP Script

• Note that inside the echo command, it is similar
  to writing code on regular HTML.
• Remember that the PHP script will be
  pre-processed.
• Therefore when you try and view the code, it does
  not have the php scripts but rather the final
  processed text.
• Therefore, you have to upload it to the server to
  see how it looks like. If you preview, you will
  see garbage.

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Variables

• Similar to JavaScript, you can work with
  variables.
• Variables must begin with a dollar sign ().
• You can generally name a variable anything you
  like as long as it begins with a and a letter
  or a underscore _.
• For example, a good variable name might be
  firstName or first_name.
• DO NOT include blank spaces in a variable name.
• If you choose to make a variable name out of two
  or more words, I recommend using an underscore (
  _ ) between the two words or capitalizing the
  second word so the variable name is easier to
  read.

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Variables

• A variable can store integers as in
• num 5
• or it can store a decimal number as in
• price 19.99
• or it can store a string (i.e. a word or phrase)
  as in
• name 'John Doe'
• Variables in php do not need to be declared with
  specific data types

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Variables

• You can use the dot operator ( . ) to concatenate
  two strings together into one string. Remember to
  add a blank space if necessary with ' ' or " ".
  For example the following code segment will
  result in the name "John Doe" being stored in the
  variable wholeName.
• firstName 'John'
• lastName 'Doe'
• wholeName firstName . ' ' . lastName

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Using comments

• Especially when you are still new to the language
  it is good to put comments around your code
• Three ways to include a PHP comment
• Anything typed to the right of two forward
  slashes // is a comment as in // this is a
  comment
• Anything enclosed within the symbols / and / is
  a comment. This kind of comment can extend to
  multiple lines of code
• / this is a comment this is still a
  comment this is a comment /
• Anything typed to the right of a pound symbol (
  ) is a comment
• this is a comment

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Process data from a form

• PHP to access data submitted by a form
• PHP creates an array using data sent using a POST
  action request.
• To assess variables in a POST request, you can
  use the _POST array.
• e.g. ltinput type"text" name"val1" value""gt
• _POST'val1' will have the value of what you
  store in the textbox above.

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Let us put it together using formspex2.html
pex2.php

• pex2.html
• lthtmlgt
• ltheadgt lt/headgt
• ltbodygt
• ltform action "pex2.php" method"post"gt
• Enter your message
• ltinput type"text" name"msg" size"30"gt
• ltinput type"submit" value"Send"gt
• lt/formgtlt/bodygt
• lt/htmlgt

• pex2.php
• lt?php
• input_POST'msg'
• echo "You said input"
• ?gt

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pex3.html, pex3.php
Error Message 1
Error Message 2
Correct Response

• Create a form that allows you to enter your first
  and last name.
• Check that both names are not empty using PHP
  using strlen().
• The command trim(variable_name) trims any spaces
  in the beginning or end and returns the new
  string.
• The command strlen(variable_name) counts the
  number of characters in the variable_name.
• So you can combine strlen(trim(variable_name) to
  count the number of characters omitting any
  spaces in front or back.
• The if (condition) works the same as JavaScript
  eg.
• if (a b)
• echo (ltbgtHELPlt/bgt)