Crash Course of PHP Back

1. Embedding PHP in HTML

  • PHP tags:
    • XML Style: <?php echo '<p>Order processed.</p>'; ?>
    • Short Style: <? echo '<p>Order processed.</p>'; ?>
    • SCRIPT Style: <script language='php'> echo '<p>Order processed.</p>'; </script>
    • ASP Style: <% echo '<p>Order processed.</p>'; %>
<html>
<head>
    <title>Bob's Auto Parts - Order Results</title>
</head>

<body>
    <h1>Bob's Auto Parts</h1>

    <?php
        echo '<p>Order processed.</p>';
    ?>

</body>
</html>

2. PHP Statements

2.1 Whitespace
<?php echo 'hello     ' . 'world' ?>
<?php echo 'hello ' . 'world' ?>
2.2 Comments
<?php 
    echo ‘<p>Order processed.</p>'; // Start printing order
?>
<?php 
    echo ‘<p>Order processed.</p>'; # Start printing order
?>
<?php 
    echo ‘<p>Order processed.</p>'; /* Start printing order */
?>
2.3 Function
<?php
    data('H:i, jS F');    // 'H' for 24-hour format with leading zeros
                // 'i' for minutes    with leading zeros
                // 'j' for the day of the month without a leadig zero
                // 'S' for the ordinal suffix(like 'th')
                // 'F' for the full name of month
?>
2.4 Variables
  • short style: requires the register_globals configuration setting be turned on with the reson of security issue.(off by default)
  • medium style: solve the security issue.(recommended)
    • $_POST: the form was submitted via the POST method.
    • $_GET: the form was submitted via GET method.
    • $_REQUEST: th for was submitted via either POST or GET method.
  • long style: used on old server.
$var                // short style
$_POST['var']            // medium style
$HTTP_POST_VARS['var']        // long style

<?php
// create short variable names
$tireqty = $_POST['tireqty'];
$oilqty = $_POST['oilqty'];
$sparkqty = $_POST['sparkqty'];
?>
2.5 String Concatenation(字符串連接)
  • A period(.) is the string concatenation operator, which adds astrings together.
echo('Hello' . ' world');

3. Variable Types

3.1 Data Type
  • Integer
  • Float
  • String
  • Boolean
  • Array
  • Object
  • NULL: variables that have not been given a value.
  • resources: represents external resources (such as database connections)
3.2 Type Strength
  • PHP is called weakly typed, or dynamically typed language.
3.3 Variable Variables
  • To enable you to change the name of a variable dynamically.
$varname = 'tireqty';
$$varname = 5;
// equivalent to $tireqty = 5;

4. Declaring and Using Constants

define('TIREPRICE', 100);
define('OILPRICE', 10);
  • phpinfo() provides a list of PHP's predefined variables and constants, among other useful information.

5. Variable Scope

  • 6 basic scope rules in PHP:
    • Built-in superglobal variables are visible everywhere within a script.
    • Constants, once declared, are always visible globally; that is, they can be used inside and outside functions.
    • Global variables declared in a script are visible throughout that script, but not inside functions.
    • Variables inside functions that are declared as global refer to the global variables of the same name.
    • Variables created inside functions and declared as static are invisible from outside the function but keep their value between one execution of the function and the next.
    • Variables created inside functions are local to the function and cease(停止) to exist when the function terminates.
  • Some special arrays with their own rules:
    • $GLOBALS: An array of all global variables.
    • $_SERVER: An array of server environment variables.
    • $_GET: An array of variables passed to the script via the GET method.
    • $_POST: An array of variables passed to the scriptvia the POST method.
    • $_COOKIE: An array of cookie variables
    • $_FILES: An array of variables related to file uploads.
    • $_ENV: An array of environment variables.
    • $_REQUEST: An array of all user input including the contents of input including $_GET, $_POST, and $_COOKIE but not $_FILES.
    • $_SESSION: An array of session(一段時間) variables.

6. Some Operators

6.1 Reference Operator
$a = 5;
$b = $a;
$a = 7;        // $b is stll 5

$a = 5;
$b = &$a;
$a = 7;        // $b and $a are both 7
6.2 Comparison Operators
0 == 0;        // 0 == 0 will be true
0 === 0;    // 0 === 0 will be not because one can be an integer, and the other can be a string
6.3 Logical Operators

6.4 Bitwise Operators

6.5 Array Operators

6.6 The Error Suppression Operator
  • The error suppression operator (@) can be used in front of any expression to suppress(抑制) errors. (Those errors should be handled by error handling code)
  • Error message can be stored in the global variable $php_errormsg when track_errors feature enabled in php.ini.
6.7 The Execution Operator
  • a pair of backticks (``) is used to include executing commands.
$out = `ls -la`;
echo '<pre>' . $out . '</pre>';
6.8 Type Operators
class sampleClass{};
$myObject = new sampleClass();
if($myObject istanceof sampleClass)
    echo("myObject is an instance of sampleClass");

7. Variable Functions

$a = 56;
echo(gettype($a) . '<br />');
settype($a, 'double');
echo(gettype($a) . '<br />');

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