Hi,

Increment/decrement operators are unique in the sense that they operate only on variables and not on any value. The reason for this is that in addition to calculating the result value, the value of the variable itself changes as well.

IncrementDecrement Operators.doc

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Senraj.A

Hi,

Increment/decrement operators

As you can see from the previous table, there’s a difference in the value of
post- and pre-increment. However, in both cases, $var is incremented by 1. The
only difference is in the value to which the increment expression evaluates.
Example 1:
$num1 = 5;
$num2 = $num1++;// post-increment, $num2 is assigned $num1's original
➥value
print $num1; // this will print the value of $num1, which is now 6
print $num2; // this will print the value of $num2, which is the
➥original value of $num1, thus, 5

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Senraj.A

Hi,

Increment/decrement operators
Example 2:

$num1 = 5;
$num2 = ++$num1;// pre-increment, $num2 is assigned $num1's
➥incremented value
print $num1; // this will print the value of $num1, which is now 6
print $num2; // this will print the value of $num2, which is the
➥same as the value of $num1, thus, 6

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Senraj.A

Hi,

Incrementing Strings Strings (when not numeric) are incremented
in a similar way to Perl. If the last letter is alphanumeric, it is incremented by
1. If it was ‘z’, ‘Z’, or ‘9’, it is incremented to ‘a’, ‘A’, or ‘0’ respectively, and the
next alphanumeric is also incremented in the same way. If there is no next
alphanumeric, one is added to the beginning of the string as ‘a’, ‘A’, and ‘1,’
respectively. If this gives you a headache, just try and play around with it.
You’ll get the hang of it pretty quickly.

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Senraj.A

Hi,

The Cast Operators
PHP provides a C-like way to force a type conversion of a value by using the
cast operators. The operand appears on the right side of the cast operator,
and its result is the converted type according to the following table.

Cast Operators.doc

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Senraj.A

Hi,

The casting operators change the type of a value and not the type of a
variable.

For example:
--------------
$str = "5";
$num = (int) $str;
This results in $num being assigned the integer value of $str (5), but $str
remains of type string.

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Senraj.A

Hi,

The Silence Operator

The operator @ silences error messages during the evaluation process of an
expression.

for example:
-------------
with out silence operator
$obj = new sample();
$obj -> example();
with silance operator
@$ob->example();

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Senraj.A

Hi,

The One and Only Ternary Operator

One of the most elegant operators is the ?: (question mark) operator. Its format
is
truth_expr ? expr1 : expr2
The operator evaluates truth_expr and checks whether it is true. If it is,
the value of the expression evaluates to the value of expr1 (expr2 is not evaluated).
If it is false, the value of the expression evaluates to the value of expr2
(expr1 is not evaluated).

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Senraj.A

Hi,

Ternary Operator

For example, the following code snippet checks whether $a is set (using
isset()) and displays a message accordingly:
$a = 99;
$message = isset($a) ? '$a is set' : '$a is not set';
print $message;
This example prints the following:
$a is set

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Senraj.A

Hi,

FUNCTIONS

A function in PHP can be built-in or user-defined; however, they are both
called the same way.The general form of a function call is

func(arg1,arg2,…)

The number of arguments varies from one function to another. Each
argument can be any valid expression, including other function calls.

Here is a simple example of a predefined function:
$length = strlen("John");
strlen is a standard PHP function that returns the length of a string.
Therefore, $length is assigned the length of the string "John": four.

Here’s an example of a function call being used as a function argument:
$length = strlen(strlen("John"));
You probably already guessed the result of this example. First, the inner
strlen("John") is executed, which results in the integer 4. So, the code simpli-
fies to
$length = strlen(4);
strlen() expects a string, and therefore (due to PHP’s magical autoconversion
between types) converts the integer 4 to the string "4", and
thus, the resulting value of $length is 1, the length of "4".

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Senraj.A

Hi,

User-Defined Functions

The general way of defining a function is
function function_name (arg1, arg2, arg3, …)
{
statement list
}
To return a value from a function, you need to make a call to return expr
inside your function. This stops execution of the function and returns expr as
the function’s value.
The following example function accepts one argument, $x, and returns its
square:
function square ($x)
{
return $x*$x;
}
After defining this function, it can be used as an expression wherever you
desire.
For example:
print 'The square of 5 is ' . square(5);

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Senraj.A

Hi,

Function Scope

Every function has its own set of variables. Any variables used outside the
function’s definition are not accessible from within the function by default.
When a function starts, its function parameters are defined. When you use
new variables inside a function, they are defined within the function only and
don’t hang around after the function call ends. In the following example, the
variable $var is not changed by the function call:
function func ()
{
$var = 2;
}
$var = 1;
func();
print $var;

When the function func is called, the variable $var, which is assigned 2,
is only in the scope of the function and thus does not change $var outside the
function. The code snippet prints out 1.
Now what if you actually do want to access and/or change $var on the
outside? As mentioned in the “Variables” section, you can use the built-in
$GLOBALS[] array to access variables in the global scope of the script.

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Senraj.A

Hi,

the previous script the following way:
It prints the value 2.
A global keyword also enables you to declare what global variables you
want to access, causing them to be imported into the function’s scope. However,
using this keyword is not recommended for various reasons, such as misbehaving
with assigning values by reference, not supporting unset(), and so
on.
Here’s a short description of it—but please, don’t use it!
The syntax is
global $var1, $var2, ...;
Adding a global line for the previous example results in the following:
This way of writing the example also prints the number 2.

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Senraj.A

Hi,

Returning Values By Value

You can tell from the previous example that the return statement is used to
return values from functions. The return statement returns values by value,
which means that a copy of the value is created and is returned to the caller of
the function. For example:
This code prints the number 10. However, making changes to $value before
the print statement only affects $value and not the global variable $num. This is
because its value was returned by the get_global_variable_value() by value and
not by reference.

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Senraj.A

Operator Description Example Result
1) + Addition x=2 x+2
answer . 4
2) - Subtraction x=2 x-5
answer. 3
3)* Multiplication x=4 x*5
answer 20

comparison operator are like ==, !=,>, >=,===, !==
in php are many operator left operators i will discuss later.

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