Outline
- Hyper Text Preprocessor
- Variables and types
- Operators
- Selection and loop statements
- Array
- Functions and variables scopes
- Cookies and Sessions
HyperText Preprocessor (PHP)
- An open-source, server-side, HTML-embedded scripting language uses for form handling and database access.
- Syntax is similar to JavaScript.
- Variables are dynamic typing i.e. the type of a variable is set every time it it assigned a value.
- PHP scripts are either embedded in markup documents or are in files that are referenced by such documents.
Embeded PHP
<!DOCTYPE html>
<html>
<head>
<title>PHP Test</title>
</head>
<body>
<?php echo "<p>Hello World</p>"; ?>
</body>
</html>
Referenced PHP
<!DOCTYPE html>
<html>
<head>
<title>PHP Test</title>
</head>
<body>
<?php include($_SERVER["DOCUMENT_ROOT"]."/basic_php.php"); ?>
<!--different ways-->
<?php include("C:\\xampp\\htdocs\\test\\basic_php.php" ); ?>
</body>
</html>
in basic_php.php
<?php echo '<p>Hello World</p>'; ?>
Variable Name
- begin with a dollar sign ($), followed by a letter or an underscore followed by any number of letters, digits or underscore.
- Variable names are case sensitive.
- BUT reserved words or function name are not!
Variable Types
- Four scalar types: Boolean, integer, double, and string.
- No need to declare a variable, and type of a variable is set every time the variable is assigned a value.
<?php
$txt = "Hi";
$x = 5;
$y = 10.5;
echo "<p>My variables and values: txt = $txt, x = $x, y = $y</p>";
?>
<!--My variables and values: txt = Hi, x = 5, y = 10.5-->
Integer and Double Overflow
- Size is platform e.g. 32 bits or 64 bits.
<?php
$x = 9223372036854775807;
echo "<p> " . $x . "</p>";
$x = $x + 1;
echo "<p> " . $x . "</p>";
echo "<p> " . PHP_INT_MAX . "</p>";
echo "<p> " . PHP_FLOAT_MAX . "</p>";
/* only version 7.2 and above */
?>
<!--
9223372036854775807
9.2233720368548E+18
9223372036854775807
1.7976931348623E+308
-->
image.png
Interesting Facts about Types
- double : there need not be any digits before before or after the decimal point so .345 or 345. are legal.
- String :
- Single quotes stop interpolation i.e. substitution.
- Length is limited by the memory available on the computer.
- Boolean:
- zero, 0.0, empty string, and string "0" are false.
- This implies string "0.0" is true.
<?php
$txt = "Hi\n";
$n = 5;
echo "<p> " . $txt . "</p>";
$txt = 'Hi\n';
echo "<p> " . $txt . "</p>";
$txt = "Hi\n";
echo "<p> $txt </p>";
echo '<p> $txt </p>';
echo "<p> \$txt </p>";
/* like is \ is used as escape sequence */
?>
<!--
Hi
Hi\n
Hi
$txt
$txt
-->
Unassigned Variable: NULL
- An unassigned variable i.e. unbound variable, has the value NULL.
- NULL is coerced to a value depending on the context of use, e.g. 0 if number, empty string if string.
<?php
$txt = "Hi";
$x = 5;
$y = 10.5;
$e;
$b = false;
echo $x + $e + $y;
/* here $e is treated as zero */
echo "<p> $txt" . $e . "$txt</p>";
/* here $e is treated as empty string */
echo "<p>" . ($e ? "true" : "false") . "</p>";
/* false if it is empty string or string 0, otherwise true */
$a = IsSet($e);
/* IsSet check if $e has been assigned a value */
echo $a ? "true" : "false";
echo "<p>" . (($b == $e) ? "true" : "false") . "</p>";
?>
<!--
Notice: Undefined variable: e in C:\xampp\htdocs\test\basic_php.php on line 64
15.5
Notice: Undefined variable: e in C:\xampp\htdocs\test\basic_php.php on line 67
HiHi
Notice: Undefined variable: e in C:\xampp\htdocs\test\basic_php.php on line 70
false
false
Notice: Undefined variable: e in C:\xampp\htdocs\test\basic_php.php on line 77
true
-->
- Empty string or string "0" is false, otherwise is true.
- IsSet($var) can be used to check if a value has been assigned to the variable.
Arithmetic Operators
- Arithmetic operators have the usual meanings, but ** is exponential.
3/2 => 1.5 float(auto)
mod % => using integer (auto) => integer
<?php
$txt = "Hi";
$x = 5;
$y = 10.5;
$b = true;
$e;
echo "<p>My variables and values: txt = $txt, x = $x,
y = $y, b = $b </p>";
/*My variables and values: txt = Hi, x = 5, y = 10.5, b = 1 */
echo "<p>x + y = $x + $y</p>";
/*x + y = 5 + 10.5 */
echo "<p>x + y = ";
echo $x + $y;
echo "</p>";
/*x + y = 15.5*/
echo "<p>x + y = " . ($x + $y) . "</p>";
/*x + y = 15.5 */
echo "<p>x + y = " . $x + $y . "</p>";
/* no brackets ... bad idea!! */
/*10.5 */
unset($y);
echo "<p>x + y = " . ($x + $y) . "</p>";
/*Undefined variable: y */
/* x + y = 5*/
?>
Arithmetic operators
String Operations
- Use . to catenate, .= to append.
- String can be treated like array by using { ... }.
String operators
Type Conersions
- Implicit conversions using coercions e.g. double to integer for modulus -> fractional part is dropped.
- Explicit conversions: using type casting, intval or doubleval or strval, and settype.
- Type checking :
- is _int, int_integer, is_long
- is_double, is_float, is_real
- is_bool, is_string, is_array, is_object
<?php
$txt = "Hello world!";
echo $txt{6}.$txt{4}.$txt{6}; //wow
$txt = "1.5";
$n = 1.234;
echo "<p>" . ($n + $txt) . "</p>"; //2.734
/* string coerced into double */
$txt = "h1e5";
$n = 1.234;
echo "<p>" . ($n + $txt) . "</p>"; //1.234
/* string that does not begin with a sign or a digit,
conversion fails, and zero is used */
$txt = "1e5h"; //100000
$n = 1.234;
echo "<p>" . ($n + $txt) . "</p>"; //100001.234
/* non numeric characters following the number in the string
are ignored */
echo "<p>" . (int)$n . "</p>"; //1
echo "<p>" . intval($n) . "</p>"; //1
echo "<p>" . gettype($n) . "</p>"; //double
echo "<p>" . settype($n, "integer") . "</p>"; //1
echo "<p>" . gettype($n) . "</p>"; //integer
?>
Print and echo
-
print is similar to echo, but print has a return value of 1 and echo can take multiple parameters.
echo "This ", "string ", "was ", "made ", "with multiple parameters." - print can be used with or without parentheses.
print (47);print expects string, so this has no error due to coercion.
print "some apples are red <br/> No Kumquats are <br/>";
printf
- display formatted output.
- Examples of format specifiers : %s, %d, %f
printf(liternal_string, param1, param2,...)
%10s- a character string field of 10 characters
%6d- an integer field of six digits
%5.2f- a float or double field of five spaces, with two digits to the right.
$day = "Tuesday";
$high = 79;
printf("The high on %7s was %3d", $day, $high);
Relational Operators
-
>, <, >=, <=, !=, ==, ===
"3" == 3true"3"===3false - If a string is compared with a number and the string can be converted to a number, then the string will be converted to a number.
- If the string cannot be converted, then the number will be converted to a string.
- If both operands are strings that can be converted to numbers, both will be converted and numeric comparison will be done.
- If this is not desired, using
strcmp.
- If this is not desired, using
Boolean Operators
- There are 6 Boolean operators:
and, or, xor, !, &&, and || - and and or do the same job as && and || but has a lower precedence.
Selection Statements
- Switch: control and case expressions can be integer, double, or string.
Loop statements
- To terminate execution of a loop use break.
- To skip the remainder of the current iteration use continue.
Example: HTML, CSS and PHP
<!DOCTYPE html>
<html>
<head>
<title>PHP Table</title>
<style type = "text/css">
td, th, table {
border: thin solid black;
}
tr {
text-align: center;
}
</style>
</head>
<body>
<table>
<caption> Powers table </caption>
<tr>
<th> Number </th>
<th> Square Root </th>
<th> Square </th>
<th> Cube </th>
<th> Quad </th>
</tr>
<?php
for ($number = 1; $number <=10; $number++)
{
$root = sqrt($number);
$square = pow($number, 2);
$cube = pow($number, 3);
$quad = pow($number, 4);
print("<tr> <td> $number </td>");
print("<td> $root </td> <td> $square </td>");
print("<td> $cube </td> <td> $quad </td> </tr>");
}
?>
</table>
</body>
</html>
Table
Array
Elements of an array do not need to be of the same type.
Creating an array by assigning values:
$list[0] = 17;
$list[1] = "Today is my birthday!"
$list[] = 42;The key for this element is 2.Creating an array using **array ** construct:
//traditional array
$list = array(17, 24, 45, 91);
// Non-traditional array with different keys.
//key =>value
$list = array(1 => 17, 2 => 24, 3 => 42, 4 =>91);
$ages = array("Joe" => 42, "Mary" => 41, "Bif" => 17);
$stuff = array("make" => "Cessna", "model" => "C210", "year" => 1960, 3 =>"sold");
Assigning Values to Array
- The list construct can be used to assign multiple elements of an array to scalar variables in one statement.
<?php
$ages = array("Joe" => 42, "Mary" => 41, "Bif" => 17);
foreach($ages as $temp)
{
print("$temp <br />");
}
/*
42
41
17
*/
$ages["Mary"] = 29;
foreach($ages as $temp)
{
print("$temp <br />");
}
/*
42
29
17
*/
$primes = array(7, 9, 11);
$a = 1;
$b = 2;
$c = 3;
echo "$a $b $c <br />"; // 1 2 3
list($a, $b, $c) = $primes;// only traditional array will work
print("$a $b $c <br />"); //7 9 11
list($a, $b, $c) = $ages;
print("$a $b $c <br />");
/* does not work for non traditional array
nothing will comming up */
?>
Functions that Deal with Array
<?php
$primes = array(7, 9, 11, 13);
foreach($primes as $temp)
{
print("$temp <br />");
}
/*
7
9
11
13
*/
$k = array_keys($primes);
$v = array_values($primes);
$l = sizeof($primes);
print "<p> keys </p>";
foreach($k as $temp)
{
print("$temp <br />");
}
/*
0
1
2
3
*/
print "<p> values </p>";
foreach($v as $temp)
{
print("$temp <br />");
}
/*
7
9
11
13
*/
print "<p> $l </p>"; //size of => 4
if(array_key_exists(2, $primes))
{
print "<p> Exist </p>";
}
else
{
print "<p> Not exist </p>";
}
//Exist
print "<p> unset element #2 </p>";
unset($primes[2]);
// Not exist
if(array_key_exists(2, $primes))
{
print "<p> Exist </p>";
}
else
{
print "<p> Not exist </p>";
}
$k = array_keys($primes);
$v = array_values($primes);
$l = sizeof($primes);
print "<p> $l </p>"; // 3
foreach($primes as $temp)
{
print("$temp <br />");
}
/*
7
9
13
*/
print "<p> keys </p>";
foreach($k as $temp)
{
print("$temp <br />");
}
/*
0
1
3
*/
print "<p> values </p>";
foreach($v as $temp)
{
print("$temp <br />");
}
/*
7
9
13
*/
?>
Functions that Deal with Array(2)
<?php
$str = "Are you ready for this?";
$word = explode(" ", $str); // split the words out of string
foreach($word as $temp)
{
print("$temp <br />");
}
$word = array("Not", "really");
$str = implode(" ", $word); // put it in a string
print "$str <br />";
/*
Are
you
ready
for
this?
Not really
*/
?>
current - Array's Internal Pointer
- When current points at the last element of the array, next returns false.
- current is a pointer points to current position.
- Obviously, if your array store false values, the loop iterations will stop when the value of current is false.
$cities = array("Hoboken", "Chicago", "Moab", "Atlantis");
$city = current($cities);
/*in the beginning at the time. current will point to the first element.*/
print("The first city is $city <br />");
while ($city = next($cities))
/*move the pointer to the next */
print("$city <br />");
each and current Functions
- The each function returns a two-element array consisting of the key and the value of the current element.
- each returns the element being referenced by the current pointer and then moves that pointer.
- next first moves the current pointer and then returns the value being referenced.
$salaries = array("Mike"=>42500, "Jerry" => 51250, "Fred" =>37920);
while ($employee = each($salaries)){
$name = $employee["key"];
$salary = $employee["value"];
print("The salary of $name is $salary <br />");
}
/*
The salary of Mike is 42500.
The salary of Jerry is 51250.
The salary of Fred is 37920.
*/
prev, reset and end Funcitons
$people = array("Peter", "Joe", "Glenn", "Cleveland");
echo current($people) . "<br />"; //Peter
echo next($people) . "<br />"; //Joe
echo current($people) . "<br / >"; //Joe
echo prev($people) . "<br />"; //Peter
echo end($people) . "<br />"; //Cleveland
echo prev($people) . "<br />"; //Glenn
echo current($people) . "<br / >"; //Glenn
echo reset($people) . "<br />"; //Peter
echo next($people) . "<br />"; //Joe
Implementing Stack
- array_push add one or more elements.
- array_pop deletes last element, returns the element or return null if array is empty.
$a = array("red", "green");
array_push($a, "blue", "yellow");
print_r($a);
/*red green blue yellow*/
$a = array("red", "green", "blue");
b = array_pop ($a); //b = "blue"
print_r($a);
// red green
foreach
- In foreach, the current pointer is implicitly initialized with reset i.e. the first element.
foreach($list as $temp)
print("$stemp <br />")
- You can also get key and value from the array using:
$lows = array("Mon" => 23, "Tue" => 18,"Wed" => 27);
foreach ($lows as $day => $temp)
print("The low temperature on $day was $temp <br />");
Sorting Array
- If an array has both string and numeric values, the string values migrate to the beginning in alphabetical order, and then the numeric values follow in ascending order.
- sort: replace keys with 0, 1, 2
- asort: keep the original key-value associations.
- ksort: sort by keys, and maintain key-value associations.
- rsort, arsort, krsort :sort in reverse order.
<!DOCTYPE html>
<html lang = "en">
<head>
<title> Sorting </title>
<meta charset = "utf-8" />
</head>
<body>
<?php
$original = array("Fred" => 31, "Al" => 27, "Gandalf" => "wizard", "Betty" => 42, "Frodo" => "hobbit");
?>
<h4> Original Array </h4>
<?php
foreach ($original as $key => $value)
{
print("[$key] => $value <br />");
}
$new = $original;
sort($new);
?>
<!--
Original Array
[Fred] => 31
[Al] => 27
[Gandalf] => wizard
[Betty] => 42
[Frodo] => hobbit
-->
<h4> Array sorted with sort </h4>
<?php
foreach ($new as $key => $value)
{
print("[$key] = $value <br />");
}
$new = $original;
asort($new);
?>
<!--
Array sorted with sort
[0] = hobbit
[1] = wizard
[2] = 27
[3] = 31
[4] = 42
-->
<h4> Array sorted with asort </h4>
<?php
foreach ($new as $key => $value)
{
print("[$key] = $value <br />");
}
$new = $original;
ksort($new);
?>
<!--
Array sorted with asort
[Frodo] = hobbit
[Gandalf] = wizard
[Al] = 27
[Fred] = 31
[Betty] = 42
-->
<h4> Array sorted with ksort </h4>
<?php
foreach ($new as $key => $value)
{
print("[$key] = $value <br />");
}
?>
<!--
Array sorted with ksort
[Al] = 27
[Betty] = 42
[Fred] = 31
[Frodo] = hobbit
[Gandalf] = wizard
-->
</body>
</html>
Functions
- Parameters are optional.
- Function's definition need not appear before the function is called.
- Function overloading is not allowed.
- Function cannot be redefined.
- Function names are not case sensitive.
- return returns a value to the caller (no return means no values is returned.)
- You can pass by value as well as pass by reference.
- the number of actual parameters does not need to match the number of formal parameters.
function foo(&$var) //"&" pass by reference , formal parameters
{
$var++;
}
$a = 5;
foo($a); // actual parameters
// $a is 6 here.
global and static Variables
- Without global, $bigsum outside of the function is hidden.
global and static
- static will only initial one time.
preg_match amd preg_split
- preg_match returns true if pattern exists.
- preg_split returns an array but operates on string.
if (preg_match ("/^PHP/", $str))
print "\$str begins with PHP <br />";
else
print "\$str does not begin with PHP <br />";
$fruit_string = "apple : orange : banana";
$fruits = preg_split("/ : /", $fruit_string);
Handling Forms
-
_GET can be used to get form values.
- POST: pass with PHP script. (cannot see.)
- GET: pass in the URL.(value can see from the URL)
POST
http://localhost:8081/test/mycal.php
<!DOCTYPE html>
<html>
<head>
<title>PHP Post</title>
</head>
<body>
<form action = "mycal.php" method = "post">
<input type = "text" name = "one" size = "30" />
<input type = "text" name = "two" size = "30" />
<input type = "submit" value = "Calculate" />
<input type = "reset" value = "Reset" />
</form>
</body>
</html>
<!--in mycal.php-->
<!DOCTYPE html>
<html>
<head>
<title>Post Process</title>
</head>
<body>
<?php
$one = $_POST["one"];
$two = $_POST["two"];
$sum = $one + $two;
print "$one + $two = $sum <br />";
?>
</body>
</html>
GET
http://localhost:8081/test/mycal.php?one=3&two=2
<!DOCTYPE html>
<html>
<head>
<title>PHP Post</title>
</head>
<body>
<form action = "mycal.php" method = “get”>
<input type = "text" name = "one" size = "30" />
<input type = "text" name = "two" size = "30" />
<input type = "submit" value = "Calculate" />
<input type = "reset" value = "Reset" />
</form>
</body>
</html>
<!--mycal.php-->
<!DOCTYPE html>
<html>
<head>
<title>Post Process</title>
</head>
<body>
<?php
$one = $_GET["one"];
$two = $_GET["two"];
$sum = $one + $two;
print "$one + $two = $sum <br />";
?>
</body>
</html>
Cookies
- A session is the time span during which a browser interacts with a particular server.
- A session beigins when a browser connects to the server and ends either when:
- The browser is terminated, or
- The server terminated the session because of client inactivity.
- HTTP is stateless, i.e no means for storing information about a session that is available to a subsequent session.
- Cookies used to identify each of the customer when visiting the website.
- A cookie is created by the server and includes small informaiton such as name and textual value.
- HTTP header can include one or more cookies.
- A cookie is given a lifetime when cookie is created, and the cookie will be deleted from the browser when the lifetime is reached.
$_COOKIE and setcookie
- setcookie takes one or more parameters: e.g. name, value, expiration time.
- If value is absent, setcookie undefines the cookie.
- A cookie MUST be created before any other HTML is created by the PHP document
<?php
//set the expiration date to one hour ago
setcookie("user", "", time() - 3600);
?>
<?php
$cookie_name = "user";
$cookie_value = "John Doe";
setcookie($cookie_name, $cookie_value, time() + (86400 * 30), "/"); //86400 = 1 day
// before any other HTML
?>
<html>
<body>
<?php
if(!isset($_COOKIE[$cookie_name])){
echo "Cookie named ' " . $cookie_name . " ' is not set!";
} else {
echo "Cookie ' " . $cookie_name . " ' is set!";
echo "Value is : " . $_COOKIE[$cookie_name];
}
?>
</body>
</html>
$_SESSION
session
session 2
Conclusions
- PHP has some similarities with C and JavaScript.
- print, echo and printf can be used to display information on the browser.
- array and it's pointers: current, prev, and next.
- foreach loop.
-
_POST
-
_SESSION.
