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Chapter 3 Introduction to PHP. By default, PHP documents end with the extension . php files ending with . htm or .html to also get parsed by the PHP processor

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Chapter 3 Introduction to PHP

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Chapter 3 Introduction to PHP


  • By default, PHP documents end with the extension .php

  • files ending with .htmor .html to also get parsed by the PHP processor

  • To trigger the PHP commands, you need to learn a new tag. The first part is: <?phpthe closing part is encountered, which looks like this: ?>

Incorporating PHP Within HTML


  • A small PHP “Hello World” program might look like

    <?php

    echo "Hello world";

    ?>

  • all the examples from this book have been archived onto a specially created companion website at http://lpmj.net

Calling the PHP Parser


  • There are two ways in which you can add comments

  • // This is a comment

  • after a line of code $x += 10; // Increment $x by 10

  • When you need multiple-line comments

    <?php

    /* This is a section

    of multiline comments

    which will not be

    interpreted */

    ?>

Using Comments


  • Semicolons

    $x += 10;

    You must place a $ in front of all variables

    <?php

    $mycounter = 1;

    $mystring = "Hello";

    $myarray = array("One", "Two", "Three");

    ?>

Basic Syntax


  • String variables $username = "Fred Smith";

    <?php // test1.php

    $username = "Fred Smith";

    echo $username;

    echo "<br />";

    $current_user = $username;

    echo $current_user;

    ?>

Understanding Variables


  • $count = 17; to store the number 17 in the variable $count

  • $count = 17.5; a floating-point number (containing a decimal point);

  • Arrays $team = array('Bill', 'Joe', 'Mike', 'Chris', 'Jim');

  • Two-dimensional arrays

    <?php

    $oxo = array(array('x', '', 'o'),

    array('o', 'o', 'x'),

    array('x', 'o', '' ));

    ?>

Numeric variables


  • four rules:

  • • Variable names must start with a letter of the alphabet or the _ (underscore) character.

  • • Variable names can contain only the characters: a-z, A-Z, 0-9, and _ (underscore).

  • • Variable names may not contain spaces. If a variable must comprise more than one word it should be separated with the _ (underscore) character. (e.g., $user_name).

  • • Variable names are case-sensitive. The variable $High_Score is not the same as the variable $high_score.

Variable naming rules


  • Operators are the mathematical, string, comparison, and logical commands such as plus, minus, times, and divide. PHP looks a lot like plain arithmetic; for instance, the following statement outputs 8:

    echo 6 + 2;

Operators


Arithmetic operators


Assignment operators


Comparison operators


Logical operators


  • The syntax to assign a value to a variable is always variable = value. Or, to reassign the value to another variable, it is other variable = variable.

  • Variable incrementing and decrementing

  • String concatenation uses the period (.) to append one string of characters to another. The simplest way to do this is as follows:

    echo "You have " . $msgs . " messages.";

Variable Assignment


  • Example 3-6. A multiline string echo statement

    <?php

    $author = "Alfred E Newman";

    echo "This is a Headline

    This is the first line.

    This is the second.

    Written by $author.";

    ?>

Multiple-Line Commands


  • Variables do not have to be declared before they are used, and that PHP always converts variables to the type required by their context when they are accessed.

Variable Typing


  • Constants are similar to variables, holding information to be accessed later, except that they are what they sound like—constant

Constants


  • echo cannot be used as part of a more complex expression, whereas print can

    $b ? print "TRUE" : print "FALSE";

  • The question mark is simply a way of interrogating whether variable $b is true or false. Whichever command is on the left of the following colon is executed if $b is true, whereas the command to the right is executed if $b is false

Echo and print Commands


  • A simple function declaration

    <?php

    function longdate($timestamp)

    {

    return date("l F jS Y", $timestamp);

    }

    ?>

Functions


  • To declare a variable as having global scope, use the keyword global

Global variables


<?php

function test()

{

static $count = 0;

echo $count;

$count++;

}

?>

A function using a static variable


PHP’ssuperglobal variables


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