PHP Rewind

What are all the OOP Features in PHP?

Object cloning
Inheritance
Interfaces
Abstract classes
Namespaces

15 Essential CSS Questions:

1. Which of the following is NOT a valid border-style property value?

dotted
inset
glazed
groove
solid

Ans: glazed

2. Which of the following is NOT a valid CSS length unit?

cm
dm
em
mm

Ans: dm
cm and mm are absolute length units. em is a font-relative length.

3. What is the CSS selector which allows you to target every element in a web page?

Ans: The universal selector (*).

4. Which CSS property allows you to hide an element but still maintain the space it occupies in the web page?

Ans: visibility or opacity

There are several ways to hide an HTML element with CSS.
Setting the visibility property of the element to hidden will hide the element. The element will still occupy space equal to its geometric size in the web page. For example, if the hidden element’s dimensions are 100x100px, you will see an empty 100x100px space in the area where the element is located. Hiding an element can also be accomplished by assigning opacity: 0 to an element.
Hiding an element without maintaining the space it occupies in the web page can be done by setting the element’s display property to none. Setting display to none renders the element as though it doesn’t exist.

5. There are 16 basic color keywords in CSS. Which of the following are NOT basic color keywords?

olive
fuchsia
cyan
aqua
maroon

Ans: cyan
cyan is a valid color keyword. But it’s not one of the basic color keywords.

6. The font-style CSS property has four different valid values. Three of these values are inherit, normal, and italic. What is one other valid value?

Ans: oblique

7. Which of the following two selectors has a higher CSS specificity?

Selector 1:

#object h2::first-letter

Selector 2:

body .item div h2::first-letter:hover

Ans: Selector 1: #object h2:first-letter

The specificity value of Selector 1 is 102. The specificity value of Selector 2 is 24.

8. What is the ideal order of the following pseudo-class selectors in a stylesheet?

:active
:hover
:link
:visited

Ans:

:link
:visited
:hover
:active

9. Which of the following CSS properties DOES NOT influence the box model?

content
padding
margin
outline
border

Ans: outline

The outline created with the outline properties is drawn “over” a box, i.e., the outline is always on top, and does not influence the position or size of the box, or of any other boxes. Therefore, displaying or suppressing outlines does not cause reflow or overflow.

10. When using media queries, which of the following is NOT a valid media type?

tv
all
voice
print
braille
tty
embossed

Ans: voice

voice is not a valid media type. Though there is a speech media type.

11. There are five generic font family values that can be assigned to the font-family property. Three of them are listed below. What are the other two generic font family values?

serif
sans-serif
monospace
?
?

Ans:

cursive
fantasy

12. What is the color keyword that will always be equal to the calculated color property value of the selected element/elements?

Ans: currentColor

Below is an example where the background-color and the border color will be equal to the color property value of .box elements:

.box {
  color: green;
  background-color: currentColor;
  border: 1px dashed currentColor;
}

The benefit of using the currentColor keyword is that we only need to change the color value in one place. We can just change the value of the color property, and the change will cascade to the other properties. This keyword works much the same way as CSS variables.

13. Which of the following is NOT a valid CSS unit?

ch
turn
px
ems
dpcm
s
hz
rem

Ans: ems

ch and rem are font-relative length units.
turn is an angle unit.
px is an absolute length unit.
dpcm is a resolution unit.
s is a time unit.
hz is a frequency unit.

14. Which of the following color keywords has NOT yet been proposed in a W3C specification?

blanchedalmond
dodgerblue
peachpuff
orchidblack
navajowhite
tomato

Ans: orchidblack

15. What is the CSS at-rule that can allow you to define the character encoding of a stylesheet?

Ans: @charset

UTF-8 should always be used as your CSS file’s character encoding. If this is the case, then you don’t need to declare a @charset rule.

How to run the multiple jquery methods within a single statement

In JQuery, this activity is called as chaining which means you can chain together actions/methods. Below snippet is the example of Jquery Chaining.

<script>
$(document).ready(function(){
    $("button").click(function(){
        $("#p1").css("color", "red").slideUp(2000).slideDown(2000);
    });
});
</script>

Use of callback function in JQuery

JavaScript statements are executed line by line. However, with effects, the next line of code can be run even though the effect is not finished. This will cause to trigger the errors.

To prevent this, you can create a callback function.

A callback function is executed after the current effect is finished.

With Callback function:

<script>
$(document).ready(function(){
    $("button").click(function(){
        $("p").hide("slow", function(){
            alert("The paragraph is now hidden");
        });
    });
});
</script>

Without Callback function:

<script>
$(document).ready(function(){
    $("button").click(function(){
        $("p").hide(1000);
        alert("The paragraph is now hidden");
    });
});
</script>

The difference between these two function is without callback function will throw the alert box before the hide event is finished.

Examples of JQuery Selectors

jQuery selectors are used to "find" (or select) HTML elements based on their id, classes, types, attributes, values of attributes and much more.

All selectors in jQuery start with the dollar sign and parentheses: $().

The jQuery element selector selects elements based on the element name.

You can select all <p> elements on a page like this:

$("p")

The jQuery #id selector uses the id attribute of an HTML tag to find the specific element.
An id should be unique within a page, so you should use the #id selector when you want to find a single, unique element.

To find an element with a specific id, write a hash character, followed by the id of the HTML element:

$("#test")

Syntax	Description
$("*")	Selects all elements
$(this)	Selects the current HTML element
$("p.intro")	Selects all <p> elements with class="intro"
$("p:first")	Selects the first <p> element
$("ul li:first")	Selects the first <li> element of the first <ul>
$("ul li:first-child")	Selects the first <li> element of every <ul>
$("[href]")	Selects all elements with an href attribute
$("a[target='_blank']")	Selects all <a> elements with a target attribute value equal to "_blank"
$("a[target!='_blank']")	Selects all <a> elements with a target attribute value NOT equal to "_blank"
$(":button")	Selects all <button> elements and <input> elements of type="button"
$("tr:even")	Selects all even <tr> elements
$("tr:odd")	Selects all odd <tr> elements

Why we are using $(document).ready(function() in jquery?

This is used to restrict any jQuery code from running before the document is finished loading or document is ready.

It is good practice to wait for the document to be fully loaded and ready before working with it.

This also allows you to have your JavaScript code before the body of your document, in the head section.

Here are some examples of actions that can fail if methods are run before the document is fully loaded:

Trying to hide an element that is not created yet
Trying to get the size of an image that is not loaded yet

Alternate Syntax instead of using document ready event

$(function(){

// jQuery methods go here...

});

Why we do not need to have text/javascript inside the script tag?

Our actual question is why we do not need to have type="text/javascript" inside the <script> tag in HTML5?

Ans: This is not required in HTML5 because javascript is the default scripting language in HTML5 and in all modern browsers!

Sample build.xml to create war file based on eclipse directory structure

Yesterday I got a chance to write sample build.xml for one of my colleague. He has default build.xml for his project which is written by someone based on random directories (similar to war directory structure). This build.xml is used to pack the directory sturctures and place it into the tomcat server webapp directory. In this type scenario he did not able to debugging his application from eclipse.

I advised them to create one more build.xml based on eclipse directory structure for production or uat deployment. For development purpose try to setup a tomcat server and debugging your application in eclipse without worrying about deployment. I provided that sample build.xml below. Please look it and provide your comments.

<?xml version="1.0" encoding="UTF-8"?>
<project name = "tems" basedir = "." default = "war">

    <property name="project-name" value="${ant.project.name}" />
    <property name="builder" value="Achappan Mahalingam" />

    <property name="war-file-name" value="${project-name}.war" />
    <property name="source-directory" value="src" />
    <property name="classes-directory" value="build/classes" />
    <property name="web-directory" value="WebContent" />
    <property name="web-xml-file" value="WebContent/WEB-INF/web.xml" />
    <property name="libs-directory" value="WebContent/WEB-INF/lib" />
    <property name="build-directory" value="build" />

    <target name = "info">
          <echo message = ""/>
          <echo message = "${project-name} Build File"/>
          <echo message = "-----------------------------------"/>
          <echo message = "Run by ${builder}"/>
       </target>

    <target name="war" depends="info">
        <mkdir dir="${build-directory}" />
        <delete file="${build-directory}/${war-file-name}" />
        <war warfile="${build-directory}/${war-file-name}" webxml="${web-xml-file}">
            <classes dir="${classes-directory}" />
            <fileset dir="${web-directory}">
                <exclude name="WEB-INF/web.xml" />
            </fileset>
        </war>
    </target>
</project>

What is the use of ob_start function in php? Tell me shortly to understand better.

By using ob_start(), the page and headers aren't sent to the browser until they've loaded completely, or until we call ob_end_flush().

Error: The used table type doesn't support FULLTEXT indexes?

Wow! I got this error when i am creating a below table with FULLTEXT indices. The reason for this exception is "Full-Text Search is supported only with MyISAM Engine before MySQL version 5.6"

CREATE TABLE comment
(
    commentid int unsigned NOT NULL AUTO_INCREMENT,
    userid int unsigned NOT NULL,
    comment text NOT NULL,
    PRIMARY KEY (commentid),
    FULLTEXT KEY comment (comment)
) ;

Solution:

You specify MyISAM engine at end of the table creation.

CREATE TABLE comment
(
    commentid int unsigned NOT NULL AUTO_INCREMENT,
    userid int unsigned NOT NULL,
    comment text NOT NULL,
    PRIMARY KEY (commentid),
    FULLTEXT KEY comment (comment)
) ENGINE=MyISAM;