ITEC 325 2012fall ibarland

home—lects—exams—hws
D2L—breeze (snow day)

lect07b-sticky
sticky forms
and, the mechanics of invoking javascript validation

Javascript events for validating client-side

• N.B. doc-strings (or "here-strings"): Just like double-quoted strings, except that instead of double-quote you name the delimiter.

  $foo = 17; $body= <<<END_THE_MSG_BOD Hello from computer #$foo. This is a long email. It even has a second paragraph, whoah! We're using "heredoc" strings to to do that, which quotes <?phpEverything <!-- /* haha // ha. <b> --> // */ and END_THE_MSG_BOD ! (Well everything but the id provided at the start of the heredoc, starting a line.) Bye, END_THE_MSG_BOD;

  Like double-quoted strings, you can use variables and escape-sequences. Unlike double-quoted strings, you can use a double-quote directly. (Recall that already, php strings could span multiple lines; the big advantage of here-docs (and, now-docs¹) forms is readability.)

• The straightforward way: <form onsubmit='return myValidateFunc();'>, where myValidateFunc returns a boolean; a false-value will not cause the form to be submitted.
  (If you leave this attribute off a form tag, then it's like saying onsubmit='return true;'.
• When you use the above, it causes the browser to call a javascript method for forms,“submit()”: this is what truly causes the submission to occur.
  Note that you certainly can call someForm.submit() yourself; that's how you can get other buttons to cause a submit (e.g. hitting return on a password field).

  A common misunderstanding: “if I call someForm.submit() myself, then the browser will first look at the form's onSubmit attribute and run that”. This is false! These two are layered the other way around: the onsubmit event causes the underlying submit method to be called, not vice-versa.

• Other events: onclick, onchange, onfocus, onblur.

Sticky forms

 - sticky form:
    (a) When you make the form, include 'value=...' in the tags appropriately.
    (b) But to do this, the page that *makes* the form has to be the
         same as the page that *recives* the form!
    (c) Imagine a big if-statement:
             if (this-form-was-submitted) {
                 ...validate and print server-side error message...
                 }
           
             if (form-was-submitted && data-is-valid) {
                 ...handle the accepted form stuff...
                 }
             else {
                 ...print the form...
                 echo "<input type='text' name="lastName" value=??? maxlength=??? />
             }
     (c2) example: lect07b-sticky-form.php
             
     (d) <input type="hidden" name="i-came-from-the-form" value="true" />
     (e) You can include files:
                require         include       require_once      include_once

home—lects—exams—hws
D2L—breeze (snow day)

©2012, Ian Barland, Radford University Last modified 2012.Oct.12 (Fri)

Please mail any suggestions (incl. typos, broken links) to ibarlandradford.edu