Introduction to php

 What is PHP?
 PHP: Hypertext Preprocessor
 A server-side, cross-platform HTML
embedded scripting language
 What do I need?
1. PHP-enabled web server
2. Text editor
3. A way to get PHP scripts from your
machine to the server
What is it? and What do I need?

Basic Syntax
 Escaping from HTML
1. <?php … ?>
2. <script language=“php”> … </script>
3. <? … ?>
4. <% … %>
 For Example…
<?php
/* The world renowned first program.
Programmer: Todd Barber
Date: October 31, 2006
*/
echo “Hello World!”; #displays on the screen
// A simple program to illustrate just the basics
?>

Types
 Boolean -> TRUE or FALSE
 Integer – number of the set
Z = {..., -2, -1, 0, 1, 2, ...}
 Float -> “decimal numbers”
 String – series of characters
 Single quote (‘) – doesn’t expand variables
 Double quote (“) – does expand variables
 Array – ordered map that assigns values
to keys
 NULL – represents that a variable has no
value. NULL is the only possible value.
See http://us2.php.net/manual/en/language.types.php for all possible types and more details.

Variables
 Variables are represented by a dollar sign
followed by the name of the variable.
 The variable name is case-sensitive.
 Variable names follow the same rules as
other labels in PHP. A valid variable name
starts with a letter or underscore, followed
by any number of letters, numbers, or
underscores.
$this_is_a_valid_variable
$this-one-is-not

More Variables
 Predefined Variables
 $GLOBALS – all variables currently in
the global scope
 $_SERVER – all variables set by the
web server
 $_POST – variables provided by the
HTTP POST
 $_GET – variables provides by the
HTTP GET (in the URL)
 $_SESSION – variables currently
registered with the script’s session

More Variables - Scope
 For the most part PHP variables have a single scope
<?php
$a=1;
include ‘header_info.php’;
?>
You can reference the $a variable in the file ‘header_info.php’
<?php
$b=1;
function footer_info () {
echo $b;
}
footer_info();
?>
Nothing will output. The echo statement refers to the local scope of the variable (inside the
function.) Global variables must be declared global inside the function.

 Global Keyword
<?php
$a = 1;
$b = 2;
function Sum()
{
   global $a, $b;
   $b = $a + $b;
}
Sum();
echo $b;
?>
What is $b?
More Variables – Scope
 Passing Variables
<?php
$a = 1;
$b = 2;
function Sum ($a, $b)
{
   $b = $a + $b;
}
Sum($a, $b);
echo $b;
?>
What is $b?3 2

More Variables - Variable
This outputs
hello world hello world
 Variable names which can be set and used dynamically
<?php
$a = ‘hello’;
$$a = ‘world’;
echo “$a ${$a}”;
echo “$a $hello”;
?>
 Constants - value cannot change during the execution of the script
A constant is case-sensitive by default. By convention, constant
identifiers are always uppercase.
<?php
define (“PI”,”3.14159265358979323846”);
echo PI;
?>
This outputs
3.14159265358979323846

Operator Precedence
Associativity Operators Additional Information
non-associative new new
left [ array()
non-associative ++ -- increment/decrement
non-associative ~ - (int) (float) (string) (array) (object) @ types
non-associative instanceof types
right ! logical
left * / % arithmetic
left + - . arithmetic and string
left << >> bitwise
non-associative < <= > >= comparison
non-associative == != === !== comparison
left & bitwise and references
left ^ bitwise
left | bitwise
left && logical
left || logical
left ? : ternary
right = += -= *= /= .= %= &= |= ^= <<= >>= assignment
left and logical
left xor logical
left or logical
left , (comma) many uses

Operators
 Arithmetic
 -$a is negation
 $a + $b is addition
 $a - $b is subtraction
 $a * $b is multiplication
 $a / $b is division (always returns float)
 $a % $b is modulus
 Assignment
 $a = 5 is NOT “equal to.” It is “gets set to”
 Combined operators
 +=, -=, *=, /=, %=, .=

More Operators
 Comparison
 $a == $b is equal
 $a === $b is identical (includes type)
 $a != $b is not equal
 $a <> $b is not equal
 $a !== $b is not identical
 $a < $b is less than
 $a > $b is greater than
 $a <= $b is less than or equal to
 $a >= $b is greater than or equal to
 Conditional
 ?: is ternary – expr1 ? expr2 : expr3
 If expr1 is TRUE, the expression evaluates to expr2
 If expr1 is FALSE, the expression evaluates to expr3
 Shorthand for single expression if statements

Comparing Different Types
Operand 1 Operand 2 Result
Null or String String Convert NULL to “”, numerical or lexical
comparison
Bool or null Anything Convert to bool, FALSE<TRUE
String or
number (or
resource)
String or
number (or
resource)
Translate strings (and resources) to
numbers, usual math
Array Array Array with fewer numbers is smaller
If key from operand 1 is not found in
operand 2 then arrays are incomparable
Compare value by value
Array Anything Array is always greater

More Operators
 Error Control
 @ - suppresses any errors that may be generated
 Works on expressions – if you can take a value of it then you can
use it.
 Strings
 Concatenation (.)
 Concatenating Assignment (.=)
<$php
@include “header_info.php”; // suppress error if file doesn’t exist
$a = “Hello”; // assign value Hello to $a
$b = $a . “ World”; // $b evaluates to “Hello World”
$a .= “ World”; // $a evaluates to “Hello World”
?>

More Operators
 Increment and Decrement
 ++$a – Preincrement – Increment by one, then return $a
 $a++ - Postincrement – Return $a, then increment by one
 --$a – Predecrement - Decrement by one, then return $a
 $a-- - Postdecrement - Return $a, then decrement by one
<?php
$a = 5;
echo "Should be 5: " . $a++ . "<br />n";
echo "Should be 6: " . $a . "<br />n";
$a = 5;
echo "Should be 6: " . ++$a . "<br />n";
$a = 5;
echo "Should be 5: " . $a-- . "<br />n";
$a = 5;
echo "Should be 4: " . --$a . "<br />n";
?>

More Operators
 Logical
 $a and $b is AND – TRUE if both are
TRUE
 $a or $b is OR – TRUE if either is TRUE
 $a xor $b is XOR – TRUE if either is
TRUE, but not both
 ! $a is NOT – TRUE is $a is not TRUE
 $a && $b is AND – TRUE if both are
TRUE
 $a || $b is OR – TRUE if either is TRUE

More Operators
 Array
 $a + $b is union – appends the right side to the
left side and doesn’t overwrite variables
 $a == $b is Equal – TRUE is they have the
same key/value pairs
 $a === $b is Identity – TRUE if they have the
same key/value pairs in the same order and of
the same types
 $a != $b is Inequality – TRUE if $a is not equal
to $b
 $a <> $b – Same as Inequality above
 $a !== $b is Non-identity – TRUE if $a not
identical to $b

Array Comparisons
<?php
$a = array ("a" => "apple", "b" => "banana");
$b = array ("a" => "pear", "b" => "strawberry", "c" => "cherry");
$c = $a + $b; // Union of $a and $b
echo "Union of $a and $b: n";
var_dump ($c);
$c = $b + $a; // Union of $b and $a
echo "Union of $b and $a: n";
var_dump ($c);
?>
<?php
$a = array ("apple", "banana");
$b = array (1 => "banana", "0" => "apple");
var_dump($a == $b); // bool(true)
var_dump($a === $b); // bool(false)
?>
<?php
$a = array(1,2,3);
$b = array(1,7,8,9,10);
$c = $a + $b; // Union of $a and $b
echo "Union of $a and $b: n";
//echo $c
print_r($c);
?>

Control Structures -- if
 if – evaluates an expression to its
Boolean value – if the expression
evaluates to TRUE then the conditional
code is executed; otherwise it is ignored
<?php
$a = 5;
if ($a = 6)
echo “Hello World”;
?>
<?php
$a = 5;
if ($a == 6)
{
echo “Hello World”;
$b = 7;
}
?>
if block is executed and
displays Hello World – note the
assignment operator in the expression
if block is ignored and
nothing is done – note the
comparison operator in the expression

Control Structures - else
 else – extension of if statement that
executes code when the if expression
evaluates to FALSE
<?php
$a=3;
$b=4;
if ($a < $b)
echo “Variable A is less than B”;
else
echo “Variable B is less than A”;
?>

Control Structures - elseif
 elseif – another extension of if
<?php
$a=3;
$b=4;
if ($a < $b) {
echo “Variable A is less than B”;
} elseif ($a == $b) {
echo “Variable A has the same value as B”;
} else {
echo “Variable B is less than A”;
}
?>

Control Structures - while
 while – execute the statements as
long as the expression evaluates to
TRUE
<?php
$a=3;
while ($a==4)
{
echo “The value of a is ”.$a;
}
?>
<?php
$i = 1;
while ($i <=10)
{
echo “i is set to “.$i++;
}
?>
<?php
$j = 0;
while ($j <=10)
{
echo “j is set to “.++$j;
}
?>
Counts to
10
Counts to
11

Control Structures – do-while
 do-while – same as while except the
code chunk is guaranteed to execute
at least once
<?php
$a=3;
while ($a==4)
{
}
?>
<?php
$a=3;
do
{
} while ($a==4);
?>
Evaluates to FALSE and while
loop statement(s) are never
executed
while expression isn’t evaluated
until after at least one iteration
of the do-while statements. This
echoes “The value of a is 3” to
the screen.

 for (expr1; expr2; expr3)
{ statement(s); }
 expr1 is evaluated unconditionally
 expr2 is evaluated at the beginning of
each iteration; continues on TRUE
 expr3 is evaluated at end of iteration
<?php
for($i=1;$i<=10;$i++)
{
echo $i.”<br />”;
}
?>
Control Structures - for
<?php
$i=1;
while ($i<=10)
{
echo $i.”<br />”;
$i++;
}
?>
functions the
same as

Control Structures - switch
 switch – the same as a series of if…
elseif statements
<?php
$i = 2;
switch ($i)
{
case 0:
echo $i;
break;
case 1:
echo $i;
break;
case 2:
echo $i;
break;
default:
echo $i;
break;
?>
<?php
$i=2;
if ($i==0)
echo $i;
elseif ($i==1)
echo $i;
elseif ($i==2)
echo $i;
?>

More switch
<?php
$i = 4;
switch ($i)
{
case 0:
case 1:
case 2:
case 3:
echo “I is less than 4”;
break;
case 4:
echo “I is equal to 4”;
break;
default:
echo “I is greater than 4”;
break;
?>
Combining cases Omitting Breaks
<?php
$i = 4;
switch ($i)
{
case 0:
case 1:
case 2:
case 3:
echo “I is less than 4”;
case 4:
echo “I is equal to 4”;
default:
echo “I is greater than 4”;
?>

Control Structures – require and include
 require – includes and evaluates a
specific file; failure results in a Fatal
Error
<?php
require ‘header.php’;
?>
 include - includes and evaluates a
specific file; failure results in a
Warning
<?php
include ‘header.php’;
?>

Control Structures –
require_once and include_once
 require_once – same as require except if
the file has already been included, it will
not be included again
<?php
require_once ‘header.php’;
?>
 include_once - same as include except if
the file has already been included, it will
not be included again
<?php
include_once ‘header.php’;
?>
 Use when the same file might be included and
evaluated more than once during a particular
execution of a script, and you want to be sure that
it is included exactly once to avoid problems with
function redefinitions, variable value
reassignments, etc.

User-defined functions
 Any valid PHP code can appear inside a
function
 Names follow the same rules as other
labels in PHP
 All functions in PHP have the global scope
<?php
function my_first_function ($arg1, $arg2, … ,$arg_n) //arguments aren’t mandatory
{
echo “PHP code goes here.”;
return $return_value; //only used when something is returned
}
my_first_function(); // example of function call with no arguments
my_first_function(1,2); // function with static arguments
my_first_function($variable); // function with a variable as an argument
}

Functions and Arguments
 Information can be passed to the
function by the argument list, a
comma separated value list of
expressions
 Arguments may be passed by:
 Value (default)
 Reference
 Default argument list
 Variable-length argument lists are
supported only in PHP4 and greater

 Passing by value examples
<?php
######### NUMBERS ###########
function add_numbers($value1, $value2)
{
echo “The numbers $value1 + $value2 equal “. $value1+$value2;
}
add_numbers(3,4); #adding 2 static numbers
add_numbers($age1,$age2); #adding 2 ages given by a user from a form
######### STRING ###########
function display_instructions()
{
echo “Text goes here. Great for text that changes often and is used many places.”;
}
display_instructions();
######### ARRAYS ###########
function add_array_values($func_array)
{
echo “The numbers $func_array[0] + $func_array[1] = “. $func_array[0] + $func_array[1];
}
$main_program_array = array(2,3);
add_array_values($array);
?>
Function Examples

More Function Examples
 Passing by Reference and Default Argument List
<?php
$dbc = OCILogon("A201","$password","$database");
function which_name($identifier,&$conn,$count="1")
{
//global $dbc;
//$conn =& $GLOBALS['dbc'];
if ($identifier == "last")
$sql = "select t100_first_name, t100_last_name from a201t100 where t100_last_name like 'Q%'";
else
$sql = "select t100_first_name, t100_last_name from a201t100 where t100_first_name like 'Q%'";
$stmt = OCIParse($conn,$sql);
OCIExecute($stmt);
while ($row=OCI_fetch_row($stmt)) {
echo "<tr><td>".$count++."</td><td>$row[0] $row[1]</td></tr>";}
OCIFreeStatement($stmt);
OCILogoff($conn);
}
echo "<table border='1' cellpadding='3’ width='30%'><tr><td>Count</td><td>Name</td></tr>n“;
which_name("first",$dbc);
echo"</table>";
?>

More Function Examples
 Passing by reference notes
 Used when you want to change the value of the
object you passed in
 I don’t know of a realistic use except when
using classes. Can be used to return more than
one value from a function (more on that later).
 Passing by default argument list
 Any defaults must be on the right side of the
argument list
 Must be a constant expression
 Uses default unless specified otherwise

Variable length argument lists
 Uses the func_num_args(), func_get_arg(), and
func_get_args() functions.
<?php
function math()
{
$numargs = func_num_args();
echo "Number of arguments: $numargsn<br />";
echo "The second side is: " . func_get_arg(1) . "<br />n";
$arg_list = func_get_args();
for ($i = 1; $i < $numargs +1; $i++) {
echo "Side $i is: " . $arg_list[$i -1] . "<br />n";
$area += $arg_list[$i -1];
}
return $area;
}
$area_of_object = math(3,4,5,6,1); // Prints 'Number of arguments: 5'
echo "The area of the object is $area_of_object";
?>

Returning values
 A value can be returned by using the
optional return() statement
 Function execution is ended
immediately and control passed back
to the line that called the function
 Returns a single variable
 could be a single number or string
 could be an array with several values

return() examples
 Single number
<?php
function square($num)
{
return $num * $num;
}
echo square(5); //displays 25
?>
 Single String
<?php
function display($string1, $string2=“World”)
{
return $string1 . $string2;
}
echo display(“Hello”,” Todd”);// displays Hello Todd
echo display(“Hello ”);//displays Hello World
?>

More return() examples
 Array – use the built-in list() function
to access the array elements
<?php
function math($num1, $num2)
{
$div = $num1 / $num2;
$mutli = $num1 * $num2;
$add = $num1 + $num2;
$sub = $num1 - $num2;
return array($div, $mutli, $add, $sub);
}
list ($d, $m, $a, $s) = math("6","2");
echo "Division: $d";
echo "<br />Multiplication:". $m;
echo "<br />Addition: $a";
echo "<br />Subtraction: $s";
?>

More return() examples
 Passing by reference to return multiple values
<?php
function split_string($input, $cut_point, &$first, &$second)
{
if(strlen($input) < $cut_point)
return false;
$first = substr($input, 0, $cut_point);
$second = substr($input, $cut_point);
return true;
}
$input_text = "abcdefghijklmnopqrstuvwxyz";
if(split_string($input_text, 30, $first_half, $second_half) != true)
{
echo "Could not split input, cut-point is entire string!<br />";
}
if(split_string($input_text, 15, $first_half, $second_half) == true)
{
echo "First segment of input: $first_half<BR>";
echo "Second segment of input: $second_half<BR>";
}
?>

Oh, by the way…
 You can also return by reference. See
http://www.php.net/manual/en/language.references.return.php for a
simple example and some explanation
 Remember variable variables? (Slide 9) PHP also allows for
variable functions
<?php
function display()
{
echo “In a function…”;
}
$variable_function = “display”;
$variable_function();
?>
 Built in Functions - http://www.php.net/manual/en/funcref.php
 Sessions - http://www.php.net/manual/en/ref.session.php
 Oracle - http://www.php.net/manual/en/ref.oci8.php
 Strings - http://www.php.net/manual/en/ref.strings.php
 Date & Time - http://www.php.net/manual/en/ref.datetime.php
 Arrays - http://www.php.net/manual/en/ref.array.php
 File System - http://www.php.net/manual/en/ref.filesystem.php
 PDF - http://www.php.net/manual/en/ref.filesystem.php

Introduction to php

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