PHP: For Starters
This tutorial assumes that you have a basic knowledge of programming. No PHP Knowledge required.
I. Basic Syntax
All PHP Scripts start with one of 3 things: <?php or <? or <%
and End with one of 2 things: ?> or %>
NOTE: <% and %> only works if ASP tags are enabled in the server's php.ini! <?php is recommended over all.
Example:
PHP Code:
<?php
//PHP!
?>
PHP Code:
<%
//PHP! Deprecated
%>
You may have noticed the text prefixed with "//". This is a comment in php. Comments are ignored by the compiler and are used to help the developer understand the code. Comments in PHP can follow 3 things:
//comment - A normal one line comment
# Comment - Another one line comment
/* COMMENT!
YEP */ - A multiline comment
Example:
PHP Code:
<?php
//Comment 1
#Comment 2
/* This is a
multiline
comment. All this is
ignored
*/
?>
IMPORTANT! - All lines of code in PHP MUST END WITH a semicolon. You'll see more examples of this later. The only things that do NOT end with a semicolor are the opening and closing tags and comments
II. Variables
A variable in PHP is simple. It starts with a dollar sign ($) followed by a lowercase or uppercase letter or an underscore ($V or $v or $_v) and can contain an underscore and numbers. Here are some exampes:
$var - GOOD
$var2 - GOOD
$v_ar - GOOD
$2var - BAD
$hÜh - GOOD
Also, variable names are case sensitive so:
PHP Code:
$var = "Hi!";
$Var = "Bye!";
You would think that "Bye!" is now in $var, but its not. $var is still "Hi!" since $Var has a capital V, so its different. Be careful when writing a script about this. A good remedy is to not use similar names for variables and make it all lowercase.
NOTE: One of the wonders of PHP is that you dont have to worry about types. A variable can be an int, string, bool, array and more without you having to define it as one.
III. Math
Math in PHP is just like in other languages:
+ Add
- Subtract
* Multiply
/ Divide
% Modulus
Very very simple. Examples:
PHP Code:
<?php
$addexample = 5 + 4; //Add. Sum = 9
$subtract = $addexample - 4; //$subtract = 5
$multiply = $subtract * 2 //$multiply = 10
$divide = $multiply / 2 //$divide = 5
$mod = $divide % 2 //$mod = 1
?>
Simple huh?
Functions
Functions are again, very easy, in PHP. Here is the syntax of one:
PHP Code:
function funcName($params = $defaultVal) {
//Code
}
Lets start from the beginning on this one. Before defining any function, you must put "function " in front of it to show that it is one. Next comes the name of the function, you will use this name to call it in your code later. After that comes parenthesis and inside you can optionally put parameters. If after a param you put "= value" where value can be anything from a number to a string to a boolean value, this will be the default value if none is supplied. Otherwise if there is no default value and the function is called and no value is given for that parameter, PHP gives a fatal error. Here is a working example using a function:
PHP Code:
<?php
//Pythagoreus theorem:
function thmPythag($a, $b) {
return sqrt($a^2 + $b^2);
}
$num1 = 3;
$num2 = 4;
$hypot = thmPythag($num1, $num2); //$hypot = 5
?>
In the above example, 2 numbers are given to the function thmPythag which uses the Pythagoreus theorem to give the length of the hypotenuse of a right triangle. You may notice a couple things you havent learned yet:
return and sqrt.
Sqrt is just a built in function in PHP to find the square root of a float.
Return is used in a function to return a value! In VB its like this:
Code:
Function myFunc() as Integer
myFunc = 5
End Function
In PHP:
PHP Code:
function myFunc() {
return 5;
}
IV. Scope
Have you ever heard of the term Scope? Local Scope? Global Scope? Well if not, I am going to explain them now. Whenever you init a variable, it is put into LOCAL scope. This means that it can only be used in that scope. A scope is defined using brackets {}. Example:
PHP Code:
<?php
$var = "hi!";
function scope() {
$myvar = $var;
return $myvar;
}
?>
If scope() was called, the return value would be blank. Why? Because $var was initialized outside of scope()'s scope. To use $var, you would have to put it into GLOBAL scope like so:
PHP Code:
<?php
$var = "hi!";
function scope() {
global $var;
$myvar = $var;
return $myvar;
}
?>
Now if you called scope(), it would return "hi!" That is a very basic example of scope, I may make a more detailed and advanced scope tutorial somewhere down the road, but for your sake, the above will do, for now.
V. Control Structures
i. If Structure
An if structure will compare an expression and if it results in TRUE, it'll execute the code following it, otherwise, it'll skip it. Syntax:
PHP Code:
if (expression)
code
This is good for one line of code, if you need your code to span multiply lines after an if, use brackets:
PHP Code:
if (expression) {
code
morecode
}
You can use many operators in the expression area of an if statement:
> - Greater than
< - Less than
>= - Greater than or equal to
<= - Less than or equal to
== - equal to
!= - not equal to
! - not
&& - And
|| - OR
^ - XOR
NOTE: In PHP, = is not the same as ==. What = tells PHP is "Set the value of the right side to the left side" and == tells PHP "Compare the value of the left side with the right side, if they are the same, return TRUE, else, return FALSE"
Here are examples of each operator:
PHP Code:
<?php
$num1 = 5;
$num2 = 10;
if ($num1 > $num2)
//Greater
if ($num1 < $num2)
//Less than
if ($num1 >= $num2)
//Greater than or equal to
if ($num1 <= $num2)
//Less than or equal to
if ($num1 == $num2)
//Both the same
if ($num1 != $num2)
//Not the same
if (!$num1) {
//$num1 = True (anything not 0)
if ($num1 && $num2) {
//Both are true
if (($num1 > $num2) || ($num1 == $num2))
//Greater than or equal to (not using >=)
?>
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Originally Posted by Auvee
