ITEC 325 2011fall ibarland

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php-ch03
PHP and forms
chapter 3

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

• HTML tags for Input Fields
  • check boxes

    <input type='checkbox' name='cb1' value='milk' id='cbOne' checked='checked' />

  • text fields,

    <input type='text' name='txt1' size='10' maxlength='8' id='txtone' />

  • radio buttons

    <input type='radio' name='age' value='over50' /> <br/> <input type='radio' name='age' value='30to50' /> <br/> <input type='radio' name='age' value='under30' /> <br/>

    
    
    
    
    The variable "age" will be set to one of the three values.
    (A second set of unrelated radio buttons would share a different name attribute.)
  • textareas:

    <textarea name='comments' rows='3' cols='30'> Initial Contents </textarea>

    Initial Contents
    Note that this isn't an input tag — text areas get their own tag type, “textarea”.

    (I'm not really sure why text areas are different from from checkboxes/radio-buttons/text-fields¹. It'd seem more sensible to either have a single tag input with attributes for every possible type of input-widget, or have each type of input-widget be its own stand-alone tag. But going half-and-half on the issue only confuses me.)

  • Select Boxes (drop-down)

    <select name='title'> <option value = 'mr'>Mr.</option> <option value = 'ms'>Ms.</option> <option value = 'mrs'>Mrs.</option> <option value = 'miss'>Miss</option> </select>

    Mr. Ms. Mrs. Miss
  • Submit button:

    <input type='submit' value='Submit Data to Server' />

  • Reset button:

    <input type='reset' value='Clear Form' />

• GET & POST methods

  Q: But how is information communicated from a web form (pure html) to a php program?
  A: When you click 'submit', the HTML makes a page-request to the page specified by the form's "action" attribute. (Presumably it's a php page.) The page-request incudes extra information about what html input fields had been selected, etc.. The server gets that request and invokes the php file as normal, but it also pre-initializes an array of values for the program — and it fills that array with the extra information contained in the page-request.

  • GET - form data is sent to the server appended to the server script URL
    In the server script, data is retrieved via the super global associative array $_GET.
  • POST - form data is embedded in the http request header
    Server script - $_POST
  When to use which?:
  • GET requests can be bookmarked;
  • GET requests can't be too long (not > 1000s of characters?; think text-submit boxes)
  • POST requests are more secure against casual looking over the shoulder (but still vulnerable to packet sniffing etc.)
  • When refreshing a page created via POST, browsers tend to respond: “Refreshing will cause the page to re-submit; do you really want to do this?”
  • Possible guideline (?): If the page is changing a database's contents, use POST.
  • Many people suggest using POST as default.
  • Explore: How does a newspaper handle it? nytimes. Discuss: When might you choose to use post/get vs. could just have a separate URL for each result, e.g. different xkcd strips.
• Form Example
  • Simple Form Example
    php-ch03-form-example-submit.php
• PHP Error Types

  Notice

  Non-fatal error that may or may not be indicative of a problem.
  E.g., Referring to a variable that has no value.

  Warning

  Nonfatal error that is most likely problematic.
  E.g., Misusing a function.

  Parse error

  Fatal error caused by a syntactic mistake.
  E.g., Omission of a semicolon or an imbalance of quotation marks, braces, or parentheses.

  Error

  A general fatal error.
  E.g., out of memory.

• Error Reporting Constants
  • E_NOTICE
  • E_WARNING
  • E_PARSE
  • E_ERROR
  • E_ALL
  • E_STRICT (the only one not supported by E_ALL; warns of things which might not be future compatible, etc.

  As we saw, we can combine values (to use as an argument to error_report( $level )) by bitwise-ORing (“|”) various constants. legal error flags; It is recommended to use error_report(E_ALL|E_STRICT).

  See also various error functions.

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©2011, Ian Barland, Radford University Last modified 2011.Sep.16 (Fri)

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