web app development_php_05
Post on 07-Nov-2014
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hasen@microcis.net July 07, 2013 Hassen poreya Trainer, Cresco Solution
Afghanistan Workforce Development Program
PHP Operators, Expressions, Control Statement, Loops
Operators
A symbol that tells PHP to perform a mathematical or logical operation.
Arithmetic
Logical
Bitwise
Miscellaneous
Arithmetic Operators
e.g, 27 / 3 15 % 4 23 % 6
Using a string with an Arithmetic Operator
<?php
$foo = "0"; // $foo is string
$foo = $foo + 2; // $foo is now an integer: 2
$foo = $foo + 1.3; // $foo is now a float: 3.3
$foo = 5 + "10 Books"; // $foo is integer: 15
?>
Using a string with an Arithmetic Operator
++ increment
-- decrement
If an increment operator precedes the variable, the variable will be incremented prior to evaluation of the expression; otherwise, the variable isn’t operated on until after the value of the expression is computed.
<?php
$count=1;
print($count++); //prints 1, but after print,
count is 2
print(++$count); //prints 3
?>
Logical and Relational Operators
Relational operators compare values and return either TRUE or FALSE.
Logical operators perform logical operations on TRUE and FALSE
The truth table for operators
Bitwise Operator
A bit is either 0 or 1
Bitwise operators view numbers from a binary perspective.
Operator Operation Performed
& And
| Or
Bitwise Operator
<?php
$x=14;
$y=7;
$z=$x & $y;
echo “The bitwise (AND) of 14 and 7
is: ”.$z;
?>
Other Operators
Concatenation Operator
Connect two separated values together.
<?php
$result = “Passed”;
$string = “The exam result of yours
is:”.$result;
print($string);
?>
Variable Variables with $ Operator
<?php
//set variables
$var_name = "myValue";
$myValue = 123.456;
print($$var_name . "<br />");
//prints "123.456“
?>
Assignment Operators
Precedence of Operators
<?php
print((3+2*7) . “<br>”);
//first multiplication
print(((3+2)*7) . “<br>”); //first
addition between parenthesis
?>
Expressions
Expressions
A bit of PHP that can be evaluated to produce a value.
PHP is an expression-oriented language
Everything is an expression
Expressions are combinations of identifiers and operators.
Expressions
Generally executed from left to right
Some operators are processed before others.
Use parentheses to force an operation to occur first
Two general rules
Some operators work only on certain data types.
If the operation is on a mix of an integer and a double, the integer will be converted to a double.
Expressions
PHP will even read doubles with an exponent. <?php
print((1 + "1") . "<BR>");
print((1 + " 2") . "<BR>");
print((1 + "3extra stuff") . "<BR>");
print((1 + "4.5e6") . "<BR>");
print((1 + "a7") . "<BR>");
?>
Evaluation
PHP will even read doubles with an exponent. <?php
print((1 + "1") . "<BR>"); //1 + 1 == 2
print((1 + " 2") . "<BR>"); //1 + 2 == 3
print((1 + "3extra stuff") . "<BR>"); //1 + 3 == 4
print((1 + "4.5e6") . "<BR>"); //1 + 4500000 == 4500001
print((1 + "a7") . "<BR>"); //1 + 0 == 1
//“a7” begins with a letter, PHP treats it as zero!
?>
Control Statement
TRUE and FALSE
Zero (0 and 0.0) and an empty string ("") are considered to be FALSE.
Any other numerical value or string is TRUE.
Some control statements expect a Boolean value.
The if Statement
If(condition/expression){
statements…
}
You are not forced to put an elseif or an else statement after.
<?php
if(($day == “Friday") or ($day == “Saturday"))
{
print(“University is closed");
}
?>
If, ifelse, else Statements
<?php
if ($month == "January") {
$num_month = 1;
}
elseif($month == "February")
$num_month = 2;
// March to October omitted here
elseif($month == "November")
$num_month = 11;
else
$num_month = 12;
?>
switch Statements
Switch(expression){
case case-expression
expression;
break;
case case-expression
expression;
break
…
default
expression;
}
The expression inside the switch statement is evaluated and then compared to each expression following a case expression.
A default statement works exactly like an else statement; it matches when no other case matches.
Break statement is used escape from the switch statement.
Syntax Description
switch Statement
<?php
switch($month) {
case "January":
$num_month = 1;
break;
// February to October omitted here
case "November":
$num_month = 11;
break;
default: // It must be December
$num_month = 12;
}
?>
Loops
Loops allow you to repeat lines of code based on some condition.
Example
Read lines from a file until the end is reached.
Print some text a certain number of times.
while Loop Statement
While (condition/expression){
statement;
}
It is useful when you are not sure how many times you will need to iterate your statements.
while Loop Statement
<?php
$total = 0;
$i = 1;
while ($i <= 10){
$total += $i++;
}
echo "The sum of 1 to 10 is: " .
$total;
?>
do while statement
do{
statement;
}
while(condition/expression)
Similar to while loop.
First the statement is executed, and then acts according to the condition.
do while Statement
<?php
$total = 0;
$i = 1;
do {
$total += $i++;
}
while ($i <= 10);
echo "The sum of 1 to 10 is : "
. $total;
?>
break Statement
When a break statement is encountered, the execution jumps to the outside of the loop or switch statement.
<?php
while (true){
echo “This line is printed here!”;
break;
echo “This line would never be printed”;
}
//These codes will be executed!
?>
break Statement
<?php
$i=0; $j=0;
while ($i<10){
while($j<5){
if($j==5)
break; // the loop is stopped
$j++; // once $j reaches 5
}
$i++;
}
echo „$i=‟.$i“<br>”;
echo „$j=‟.$i;
?>
continue Statement
Similar to the break statement
But only the current execution of the loop is stopped, after that loop is continued.
<?php
while ($i++<5){
if($i==2)
continue;
echo $i; //2 will not be printed.
}
?>
Let’s code something
Class exercise
Write a while loop that outputs the even numbers between 1 and 100.
Rewrite the script for Problem 1 using do while loop.
Write a while loop that outputs the numbers from 100 to 0 by 10's.
hasen@microcis.net July 07, 2013 Hassen poreya Trainer, Cresco Solution
Any Questions!
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