1 Introduction to PHP Part #2. 2 Simple PHP Script Consider the following HTML file, example.html:...

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Introduction to PHPPart #2

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Simple PHP Script

• Consider the following HTML file, example.html:

<html><head><title>My Page</title></head><body>Hello world!<p></body></html>

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Simple PHP Script• Here is an equivalent PHP script. PHP files have the extension “.php” and may

contain both HTML and PHP code, which is enclosed inside <? code ?> tags, or alternately <?php code ?>

<html><head><title>My Page</title></head><body><? print(“hello world!<p>”); ?></body></html>

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Simple PHP Script

• More interesting version, displays the date as known by the server:

<html><head><title>My Page</title></head><body><? print(“hello world! Timestamp: “ . time() . “<p>”); ?></body></html>

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PHP Time Stamp

• The “.” is used to concatenate strings

• The server parses the document and interprets code within the <? ?> tags instead of sending it directly to the client– i.e. you can write code to output the HTML you

desire

• Output of previous:

hello world! Timestamp: 1050289182

hello world! Timestamp: 1050289184Refresh twoSeconds later:

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PHP Script• Often everything is placed inside the PHP tags.

The following is equivalent; the header function specifies the MIME Type; i.e. that the document is HTML (as opposed to graphics, etc.):

<? header("Content-Type: text/html"); print("<HTML><HEAD><TITLE>My Page</TITLE>"); print("</HEAD>"); print("<BODY>"); print("hello world! Timestamp: " . time() . "<p>"); print("</BODY></HTML>");?>

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Identifiers and Data Types

• Identifiers– Case-sensitive– Same rules as Java

• Data Types– integer– double– string, surrounded by “ “ or by ‘ ‘

– Weak typing; you do not declare variables, just use them and the value assigned is the type of the variable; any old value is gone

– Can typecast just like Java• (int), (double), (string), etc.

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Variables

• A variable is an identifier prefaced by $• Example:

$x = 1; $y = 3.4; $z = $x + $y; $a = true; $s = "hello!"; print ($z . " " . $a . " " . $s);

Output: 4.4 1 hello! Note: true = non zero or not empty. False = 0 or the empty string “”

Common novice mistake: Forgetting the $

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Variables

• Interpreted; consider the following: $x = 1; $y = “x”; print($y);

Output: 1

• Often {} are used to denote variable boundaries:$x = 1;$y = “x”;print({$y});

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Form Variables

• If an HTML form invokes a PHP script, the PHP script can access all of the form variables by name

• Invoking FORM:<form method=post action=“scr.php”><input type=text name=“foo” value=“bar”>

<input type=submit value=“Submit”></form>

• Inside scr.php:print($_REQUEST['foo']); // Outputs “bar”

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Sample PHP Form<? header("Content-Type: text/html"); print("<HTML><HEAD><TITLE>My Page</TITLE>"); print("</HEAD>"); print("<BODY>"); print("foo = " . $_REQUEST[‘foo’] . ", bar = " . $_REQUEST[‘bar’] . "<P>"); print("<form method=post action=\"example.php\">"); print("<input type=text name=\"foo\" value=\"zot\">"); print("<input type=hidden name=\"bar\" value=3>"); print("<input type=submit>"); print("</form>"); print("</BODY></HTML>");?>

Note: \” escape characterCould also use ‘ instead

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Sample PHP Form

• First load:

• Upon submit:

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Web browser

• What the web browser receives after the first load. Note that we see no PHP code:

<HTML><HEAD><TITLE>My Page</TITLE></HEAD><BODY>foo = , bar = <P><form method=post action="example.php"><input type=text name="foo" value="zot"><input type=hidden name="bar" value=3><input type=submit></form></BODY></HTML>

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GET and POST• One way to hide the printing of variables when the

code is first loaded is to detect if the program is invoked via GET or POST

<? header("Content-Type: text/html"); print("<HTML><HEAD><TITLE>My Page</TITLE>"); print("</HEAD>"); print("<BODY>"); if ($_SERVER['REQUEST_METHOD'] == ‘POST') { print("foo = " . $_REQUEST[‘foo’] . ", bar = " . $_REQUEST[‘bar’] . "<P>"); } print("<form method=post action=\"example.php\">"); print("<input type=text name=\"foo\" value=\"zot\">"); print("<input type=hidden name=\"bar\" value=3>"); print("<input type=submit>"); print("</form>"); print("</BODY></HTML>");?>

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Operators

• Same operators available as in Java:+, -, *, /, %, ++, -- (both pre/post)

+=, -=, *=, etc.

<, >, <=, >=, ==, !=, &&, ||, XOR, !

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Assignments

• PHP will convert types for you to make assignments work

• Examples:print(1 + "2"); // 3

print("3x" + 10.5); // 13.5

$s = "hello" . 55;

print("$s<p>"); // hello55

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Arrays

• Arrays in PHP are more like hash tables, i.e. associative arrays– The key doesn’t have to be an integer

• 1D arrays– Use [] to access each element, starting at 0– Ex:

$arr[0] = “hello”;$arr[1] = “there”;$arr[2] = “zot”;$i=0;print(“$arr[$i] whats up!<p>”); // Outputs : hello whats up!

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Arrays

• Often we just want to add data to the end of the array, we can do so by entering nothing in the brackets:

$arr[] = “hello”;

$arr[] = “there”;

$arr[] = “zot”;

print(“$arr[2]!<p>”); // Outputs : zot!

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Array Functions

• There are many array functions; here are just a few:

count($arr); // Returns # items in the arraysort($arr); // Sorts arrayarray_unique($arr); // Returns $arr without duplicates

print_r($var); // Prints contents of a variable // useful for outputting an entire

array // as HTML

in_array($val, $arr) // Returns true if $val in $arr

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Multi-Dimensional Arrays

• To make multi-dimensional arrays just add more brackets:

$arr[0][0]=1;

$arr[0][1]=2;

$arr[1][0]=3;

..etc.

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Arrays with Strings as Key

• So far we’ve only seen arrays used with integers as the index• PHP also allows us to use strings as the index, making the

array more like a hash table• Example:

$fat[“big mac”] = 34;$fat[“quarter pounder”]=48;$fat[“filet o fish”]=26;$fat[“large fries”]=26;print(“Large fries have “ . $fat[“large fries”] . “ grams of fat.”);

// Output : Large fries have 26 grams of fat

Source: www.mcdonalds.com

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Iterating through Arrays with foreach

• PHP provides an easy way to iterate over an array with the foreach clause:

• Format: foreach ($arr as $key=>$value) { … }

• Previous example:

foreach($fat as $key=>$value)

{

print(“$key has $value grams of fat.<p>”);

}

Output:

big mac has 34 grams of fat. quarter pounder has 48 grams of fat. filet o fish has 26 grams of fat. large fries has 26 grams of fat.

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Foreach

• Can use foreach on integers too:

$arr[]="foo"; $arr[]="bar"; $arr[]="zot"; foreach ($arr as $key=>$value) { print("at $key the value is $value<br>"); }

Output: at 0 the value is fooat 1 the value is barat 2 the value is zot

If only want the value,can ignore the $key variable

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Control Statements

• In addition to foreach, we have available our typical control statements

– If– While– Break/continue – Do-while– For loop

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IF statement

• Format:

if (expression1){

// Executed if expression1 true}elseif (expression2){

// Executed if expression1 false expresson2 true}…else{

// Executed if above expressions false}

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While Loop

• Format:

while (expression)

{

// executed as long as expression true

}

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Do-While

• Format:

do

{

// executed as long as expression true

// always executed at least once

}

while (expression);

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For Loop

• Format:

for (initialization; expression; increment)

{

// Executed as long as expression true

}

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Control Example

srand(time()); // Seed random # generator with time

for ($i=0; $i<100; $i++) { $arr[]=rand(0,10); // Random number 0-10, inclusive } $i=0; while ($i<=10) { // Initialize array of counters to 0 $count[$i++]=0; } // Count the number of times we see each value foreach ($arr as $key=>$value) { $count[$value]++; } // Output results foreach ($count as $key=>$value) { print("$key appeared $value times.<br>"); }

Counts # of random numbers generated between 0-10

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Output

0 appeared 9 times.1 appeared 9 times.2 appeared 11 times.3 appeared 14 times.4 appeared 6 times.5 appeared 7 times.6 appeared 8 times.7 appeared 11 times.8 appeared 5 times.9 appeared 9 times.10 appeared 11 times.

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Functions

• To declare a function:

function function_name(arg1, arg2, …) {

// Code// Optional: return (value);

}

Unlike most languages, no need for a return type since PHP is weakly typed

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Function Example: Factorial

function fact($n)

{

if ($n <= 1) return 1;

return ($n * fact($n-1));

}

print(fact(5)); // Outputs 120

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Scoping

• Variables defined in a function are local to that function only and by default variables are pass by value

function foo($x,$y){ $z=1; $x=$y + $z; print($x); // Outputs 21}

$x=10;$y=20;foo($x,$y);print(“$x $y<p>”); // Outputs 10 20

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Arrays: Also Pass By Valuefunction foo($x){ $x[0]=10;

print_r($x); Array ( [0] => 10 [1] => 2 [2] => 3 ) print("<p>");}

$x[0]=1; $x[1]=2; $x[2]=3;

print_r($x); Array ( [0] => 1 [1] => 2 [2] => 3 ) print("<p>"); foo($x);

print_r($x); Array ( [0] => 1 [1] => 2 [2] => 3 ) print("<p>"); Not changed!

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Pass by Reference

• To pass a parameter by reference, use & in the parameter list

function foo(&$x,$y){ $z=1; $x=$y + $z; print($x); // Outputs 21}

$x=10;$y=20;foo($x,$y);print(“$x $y<p>”); // Outputs 21 20

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Dynamic Functions

• Functions can be invoked dynamically too

• Useful for passing a function as an argument to be invoked later

function foo() { print("Hi<p>"); }

$x="foo"; $x(); // Outputs “Hi”

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Classes & Objects

• PHP supports classes and inheritance• All instance variables are public in PHP 4 (PHP 5 allows private,

protected)• Format for defining a class; the extends portion is optional

class name extends base-class{

var varName;…function name() {… constructor code …}function methodName() { … code … }

…}

• To access a variable or function, use $obj->var (no $ in front of the var)• To access instance variables inside the class, use $this->var

needed to differentiate between member var and a new local var

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Class Example class user { var $name; var $password; function user($n, $p) { $this->name=$n; $this->password=$p; } function getSalary() { // if this was real, we might // look this up in a database or something return 50000; } }

$joe = new user("Joe Schmo","secret"); print($joe->name . " - " . $joe->password . "<p>"); print($joe->getSalary() . "<p>");

Output:

Joe Schmo - secret

50000

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Objects in PHP 4

• Assigning an object makes a new copy, not a reference like Java:

$joe = new user("Joe Schmo","secret"); $fred = $joe; $joe->password = "a4j1%"; print_r($joe); // user Object ( [name] => Joe Schmo [password] => a4j1% ) print("<p>"); print_r($fred); // user Object ( [name] => Joe Schmo [password] => secret ) print("<p>");

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Objects in PHP 5

• Assigning an object makes a reference to the existing object, like Java:

$joe = new user("Joe Schmo","secret"); $fred = $joe; $joe->password = "a4j1%"; print_r($joe); // user Object ( [name] => Joe Schmo [password] => a4j1% ) print("<p>"); print_r($fred); // user Object ( [name] => Joe Schmo [password] => a4j1% ) print("<p>");

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Other new items in PHP 5

• Mostly improvements in OOP model– Abstract classes and methods– Destructors– Cloning– instanceof– Reflection

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Using PHP

• Here we will focus on additional functions that will be helpful for you to complete the homework assignment

– Type Checking• is_array, is_string, is_long, is_double

– Useful string functions• strlen, implode, explode, substr, strstr, trim, char access

– File I/O• fopen, fread, feof, fclose, fwrite

– Some examples

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Type Checking

• PHP includes several functions to determine the type of a variable since it may not be obvious what the type is due to conversions

is_int($x) // returns true if $x is an integer

is_double($x) // returns true if $x is a double

is_array($x) // returns true if $x is an array

is_string($x) // returns true if $x is a string

is_null($x) // returns true if $x is a null

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String Functions

• We can access a string as an array to retrieve individual characters:

$s=“hithere”;$z = $s[0] . $s[2] . $s[4];print($z); // hte

• We can also assign characters to the string:$s[2] = “F”;print($s); // hiFhere

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Strings

• String length: strlen($s) returns the length of the string

$s="eat big macs"; for ($i=0; $i<(strlen($s)-1)/2; $i++) { $temp = $s[$i]; $s[$i] = $s[strlen($s)-$i-1]; $s[strlen($s)-$i-1] = $temp; }

print($s); // Output : scam gib tae

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Strings

• Substring: Searches a string for a substringPrototype:

string strstr (string haystack, string needle)• Returns all of haystack from the first occurrence of needle to

the end. • If needle is not found, returns FALSE.

$email = ‘[email protected]'; $domain = strstr ($email, '@');

print ($domain); // prints @acm.org

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Strings

• strtolower($s) : returns $s in lowercase$s=“AbC”;$s = strtolower($s); // $s = “abc”

• strtoupper($s) : returns $s in uppercase$s = “AbC”;$s = strtoupper($s); // $s = “ABC”

• trim($s) : returns $s with leading, trailing whitespace removed

$s = “ \n ABC \r\n”; $s = trim($s); // $s = “ABC”

Trim is useful to remove CR’s and Newlines when reading lines of data from text files or as input from a form (e.g. textbox, textarea)

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Strings

• Substring: Format:string substr (string string, int start [, int length])– Substr returns the portion of string specified by the start and length parameters.

– If start is positive, the returned string will start at the start'th position in string, counting from zero. For instance, in the string 'abcdef', the character at position 0 is 'a', the character at position 2 is 'c', and so forth.

• Examples:$rest = substr ("abcdef", 1); // returns "bcdef" $rest = substr ("abcdef", 1, 3); // returns "bcd"

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Implode

• Implode is used to concatenate elements of an array into a single string

string implode (string glue, array pieces)• Returns a string containing a string representation of all the

array elements in the same order, with the glue string between each element.

• Examples$arr[]="A"; $arr[]="B"; $arr[]="C";$s = implode(",",$arr); // $s = “A,B,C”$s = implode("",$arr); // $s = “ABC”

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Explode

• Explode is used to create an array out of a string with some delimiter

array explode (string separator, string string)• Returns an array of strings, each of which is a substring of string

formed by splitting it on boundaries formed by the string separator.

• Example$s="eat:large:fries";$arr = explode(":",$s);print_r($arr);print("<p>");

Output: Array ( [0] => eat [1] => large [2] => fries )

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File I/O• Opening a file: fopen• Format:

int fopen (string filename, string mode)– Filename is the complete path to the file to open; must have proper

permissions– Mode is one of the following

• 'r' - Open for reading only; place the file pointer at the beginning of the file. • 'r+' - Open for reading and writing; place the file pointer at the beginning of the

file. • 'w' - Open for writing only; place the file pointer at the beginning of the file and

truncate the file to zero length. If the file does not exist, attempt to create it. • 'w+' - Open for reading and writing; place the file pointer at the beginning of

the file and truncate the file to zero length. If the file does not exist, attempt to create it.

• 'a' - Open for writing only; place the file pointer at the end of the file. If the file does not exist, attempt to create it.

• 'a+' - Open for reading and writing; place the file pointer at the end of the file. If the file does not exist, attempt to create it.

– Returns: a file pointer used to reference the open file

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File I/O

• Reading from a text file:string fgets (int filepointer, int length)

– Returns a string of up to length - 1 bytes read from the file pointed to by fp.

– Reading ends when length - 1 bytes have been read, on a newline (which is included in the return value), or on EOF (whichever comes first).

– We can use this function on files we have opened for reading

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File I/O

• Writing to a text file:int fwrite (int fp, string string)– fwrite() writes the contents of string to the file stream pointed to

by fp. – The file must be opened for writing

• Checking for end of filefeof(int fp)Returns true if we have reached the end, false otherwise

• Closing a filefclose(int fp)Use when done with the file and close the file pointer

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File I/O example

$fd = fopen ("/proc/cpuinfo", "r");

while (!feof ($fd)) {

$oneline = fgets($fd, 4096);

print("$oneline<br>");

}

fclose ($fd);

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fgets

• IMPORTANT – Remember that fgets returns the string WITH the newline

• This is critical if you are going to perform comparisons– You’ll get a false match if the newline is not

accounted for– Easiest technique: trim out the newlines

$oneline = trim(fgets($fp, 1024));

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Example

• Create a single PHP script that generates a form with a textarea– Allow the user to enter numbers in the textarea– Submit the form to the same script– Compute the sum of the numbers in the textarea

and print it out

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Example.php

<?phpheader("Content-Type: text/html");print("<HTML><HEAD><TITLE>My Page</TITLE>");

print("</HEAD>");print("<BODY>");

if($_SERVER['REQUEST_METHOD'] != "POST"){

// We are loading for the first time,// not receiving a form. So generate// a form allowing the user to enter// data in a text area and have it submitted// to this same scriptprint("<FORM method=post action='example.php'>");print("Enter numbers below.<p>");print("<TEXTAREA name='myData' rows=10></TEXTAREA>");print("<INPUT type=submit>");print("</FORM>");

}

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Example.phpelse{

// We are receiving data from our form// Put the text data into an array. Each// is separated by a newline, so use explode// to parse$a = explode("\n",$_REQUEST['myData']);// Here we loop through and add up the numbers$total = 0;foreach ($a as $key=>$value) {

// Each element in the array is a string,// but note that each will contain a \r// whitespace at the end, so you may wish// to trim these out. It is not really// necessary in this example but you will// probably want to trim for your homework$num = (int) trim($value);$total += $num;

}print("The sum of your numbers is $total<p>");

} print("</BODY></HTML>");?>

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Execution

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Summary

• PHP is an imperative language for the web• Similarities to C, Java, and even interpreted

languages• Can’t do everything since server side only –

sometimes coupled with client-side languages such as JavaScript

• PHP version 5 not quite backward compatible with PHP 4

• Easy to write sloppy code so one must be more disciplined in design of classes, functions, variables, HTML, documentation

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Lots More to PHP• We have only scratched the surface, but there is much more that

PHP can do– Generate graphics (gd library)– Networking, Sockets, IRC, Email– Database Access – LDAP– Regular Expressions– PDF– Java– XML– Design methodologies (e.g. FuseBox, include files)– Many more

• See the excellent resources online– www.php.net– www.phpbuilder.com– www.zend.com

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End of PHP

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