HTML5 – Doctype
The new HTML5 Doctype is <!DOCTYPE HTML>
That’s it!
my name is george phillips and i am a freelance web developer based in london
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PHP – Operators
| Operator | Discription | Example |
| Arithmatic | Basic Maths | $a + $b |
| Array | Array Union | $a + $b |
| Assignment | Assign Values | $a = $b + 36 |
| Bitwise | Manipulates bits within bytes | 12 ^ 9 |
| Comparison | Compares two values | $a < &b |
| Execution | Executes contents of back ticks | '1s -a1' |
| Increment/Decrement | Add or Subtract 1 | $a++ |
| Logical | Boolean | $a and $b |
| String | Concatenation | $a . $b |
Operators take a different number of operands.
Unary operators ($a++) or (-$a) take a single operand.
Binary operators take two ($a + $b) etc.
One Ternary which is ? x : y
Precedence (High - Low)
Operators
() |
Parentheses |
++ -- |
Increment/Decrement |
! |
Logical |
* / % |
Arithmetic |
+ - . |
Arithmetic and String |
<< >> |
Bitwise |
< <= >= > |
Comparison |
== != === !== |
Comparison |
& |
Bitwise (and reference) |
^ |
Bitwise |
| |
Logical |
&& |
Logical |
|| |
Logical |
? : |
Ternary |
= += -= *= /= %= &= != ^= <<= >>= |
Assignment |
and |
Logical |
xor |
Logical |
or |
Logical |
These are left to right except where operator precedence is in effect. So go right to left. The direction of processing is called associativity.
Operators with right to left associativity:
Operator
NEW |
Create a new objects |
! |
Logical NOT |
~ |
Bitwise NOT |
++ -- |
Increment and decrement |
+ - |
Unary and negation |
(int) |
Cast to an integer |
(double) |
Cast to a float |
(string) |
Cast to a string |
(array) |
Cast to an array |
(object) |
Cast to an object |
@ |
Inhabit error reporting |
? : |
Conditional |
= |
Assignment |
For example, lets look at the assignment separator where all three variables are set to 0.
<?php
$level = $score = $time = 0
?>
Multiple assignment is possible only if the right hard part of the expression is evaluated first, then processing continues right to left.
PHP – Literals & Variables
The simplest form of expression is a literal which means something that evaluates to itself. An expression can also be a variable, which evaluates to the value that’s been assigned to it.
<?php
$myname = "George";
$myage = 27;
echo "a: " . 73 . " <br />" // Numeric literal
echo "b: " . "Hello" . " <br />" // String literal
echo "c: " . FALSE . " <br />" // Boolean literal
echo "d: " . $myname . " <br />" // Variable string literal
echo "e: " . $myage . " <br />" // Variable numeric literal
?>
These return:
a: 73
b: Hello
c: // false so nothing
d: George
e: 27
In conjunction with operators, it’s possible to create more complex expressions that evaluate to useful results…
When you combine assignment of control-flow constructs with expressions, the result is a statement.
<?php
$daysToNewYear = 366 - $dayNumber ; // Expression
 : if ($daysToNewYear < 30 )
{
echo "Not long to go now until new year!"; //Statement
}
?>
PHP – Expressions
An expression is a combination of values, variables, operators and functions that results in a value.
y = 3(abs(2x) + 4)
In PHP
$y = 3 * (abs(2 * $x) + 4);
The value returned (y or $y in this case) can be a number, string or a Boolean value.
Boolean is TRUE or FALSE, 5 == 6 is FALSE
Uppercase Booleans can be redefined. Lowercase cannot.
Some booleans:
<?php
echo "a : [" . ( 20 < 9 ) . "] <br />",
echo "b : [" . ( 5 == 6 ) . "] <br />",
echo "c : [" . ( 1 == 0 ) . "] <br />",
echo "d : [" . ( 1 == 1 ) . "] <br />",
?>
The output of this code would be:
a: [1]
b: []
c: []
d: [1]
Notice that both expressions a and d evaluate to true, which has a value of 1. But b & c evaluated to false don’t show anything because PHP FALSE is defined as NULL or nothing.
PHP – Variable Scope
Local variables are created in and used inside a function, they can only be accessed by the same function.
Global variables can be called by any function. All your code can access them.
Static Variables can be sued to keep track of how many times a function has been called. It’s contents are not wiped when the function has ended unlike a local variable.
Superglobal variables are predefined variables and contain lots of useful information about the current running program and it’s environment.
Superglobals are often used by hackers trying to find exploits to break into your website. You should always sanitise superglobals before using them… the htmlentities function is a good way to do this.
$came_from = htmlentities( $_SERVER['HTTP_REFERRER'] );
PHP – Functions
Functions are declared like so:
<?php
function longdate($timestamp)
{
return date("l F jS Y", $timestamp);
}
?>
To output today’s date with this function, place the following in your code:
echo longdate( time() );
This call uses the built in PHP time function to fetch the current unix timestamp and passes it the the new longdate function, which returns the appropriate string the the echo command for display.
PHP – Echo vs. Print
Print is like echo but it can be used in more complex functions.
$b ? print "TRUE" : print "FALSE";
PHP – Constants
Constants are similar to variables except they are immutable. One you have defined one it’s value is set for the rest of the program and cannot be changed.
One example for a constant might be to hold the location of your server root (containing the files of your website) like this:
define("ROOT_LOCATION", "/user/local/www/");
To read it’s contents you refer to it like a variable (but it isn’t proceeded by the $):
$directory = ROOT_LOCATION;
Now when you need to run your code on a different server, you only need to change one line of code.
Use uppercase for constants. It’s good practice.
PHP – Loosely Typed
Like the headline says, PHP is loosely typed like JavaScript.
PHP – Multiple Line Commands
There are times when you need to output quite a lot of text and multiple echo statements would be messy and time consuming. There are two ways to combat this.
The first is to just put multiple line in quotes. Variables can also be assigned.
<?php
$author = "George Phillips";
echo "This is a Headline
This is line one
This is line two
Written by $author." ;
?>
Or
<?php
$author = "George Phillips";
$text = "This is a Headline
This is line one
This is line two
Written by $author.";
?>
PHP also offers a multiline sequence using the <<< operator commonly referred to as here-document or heredoc for short.
<?php
$author = "George Phillips";
echo <<<_END
This is a headline
Line one.
Line two.
Written by $author.
_END;
?>
This outputs everything between the _END tag if it were a double quoted string. So you can write entire sections of HTML in PHP code and just replace specific dynamic posts with PHP variables.
The closing _END; tag MUST appear right at the start of a new line and the only thing on the line. Not ever a comment is allowed.