PHP tutorial - basics: Difference between revisions

Revision as of 18:24, 9 February 2010

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Web technology tutorials series
Intermediate

Introduction

Learning goals

Be able to make modifications in a PHP file (in particular configuration files)

Prerequisites

Some HTML and XHTML, i.e. HTML and XHTML elements and attributes

Moving on

See web technology tutorials

Level and target population

Beginners

Remarks

This is a first version ...

PHP standards for Hypertext Preprocessor

History:

Personal Home Page Generator (Php2/FI) in the mid-nineties

PHP 3 since 1997,

PHP 4 since 1999,

PHP 5 since 2004/2005

Since PHP 3.0, the language is used to write larger web applications. PHP Version 3.0 was defined as HTML-embedded scripting language. Much of its syntax is borrowed from C, Java and Perl with a couple of unique PHP-specific features thrown in. The goal of the language is to allow web developers to write dynamically generated pages quickly. This definition remains the same in the PHP 5 FAQ.

Principle:

Analogy with JavaScript: PHP code can be mixed with HTML

BUT: The server reads the files and computes it (and end-user never can see the code)

Servers are configured to read *.php files as PHP (sometimes also *.php3, *.php4 etc.)

Purpose:

Create dynamic web pages (small applications) or program larger web applications

Links:

See PHP links

PHP features

Availability:

Free and open source (GPL)

cross-platform (Unix, Linux, BSD, MacOS X, Win32, etc.)

Installation:

can run as CGI program (external to a web server)

can run as web server module (this is the standard case, e.g. with the Apache server)

can be used as command-line scripting engine

Highlights:

good database support (Oracle, Sybase, Microsoft, MySQL, Postgres, ODBC, etc.)

good system integration (files)

complete programming language, including OO support

easy to learn

made for internet application (cookies, authentication, sessions, redirection...)

dozens of integrated libraries (LDAP, PDF, XML, GIF,...)

support for object-oriented programming since PHP 4 (PHP 5 introduced a new model)

Alternatives to PHP:

ASP (Microsoft)

JSP (Java)

Cold Fusion (Adobe)

HTML and PHP integration

PHP code is defined within an XML processing instruction

<?php ..... ?>

<?php
 echo("if you want to serve XML documents, do like this\n");
 ?>

File inclusion

Let's now introduce our first PHP code. PHP code can be spread over many files (hundreds or thousands in some larger applications).

Include:

inserts content of file when this expression is evaluated

include ("file name");

include("style.php");

Require:

inserts content of file when the php file is loaded

require ("file name");

require("my_functions.inc");

Variant (recommended):

include_once() and require_once().

Only include once, will make your application faster.

File inclusion example

http://tecfa.unige.ch/guides/php/examples/includes/

 <HTML>
   <HEAD>
     <TITLE>Simple Include Demo (21-Apr-1998)</TITLE>
 <?php include("style.text"); ?>
   </HEAD>
   <BODY>
     <H1>Simple Include Demo</H1>
 
 In this file we include a <A HREF="style.text">style sheet</A> and
     a <A HREF="footer.text">footer</A>.
     <P>
       Look at <A HREF="include1.phps">the formatted source</A>
       or the <A HREF="include1.source">unformatted one</A>
  if you want to know how this is done.
 
     <H1>Yet another styled title</H1>
     <UL>
       <LI> bullet item </LI>
       <LI> bullet item </LI>
     </UL>
 
 <?php
 /* A footer */
 include("footer.text"); 
 ?>
   </BODY>
 </HTML>

The programming language PHP

Elements of programming

Program= algorithm + data structures

Programming elements

PHP syntax

PHP looks like "C" (C, C++, Java, Perl, etc.)

Each instruction is ended with a ";"

Comments // or #, or included within /* ... */

Variables and assignments

Variables are “containers” for information.

Each identifier with a $ in front is a variable

Variables don’t need to be declared

Assignment operator: =

Simple variables

assignment

$variable = "content" ;

Illustrations:

   $a = 10;
   $name = "Patrick Ott";
   $sum = 123.456;

Display variable contents

Files:

Application	: /guides/php/examples/simple/simple-echo.php
Source (to see)	: /guides/php/examples/simple/simple-echo.phps
Source (to copy	: /guides/php/examples/simple/simple-echo.text

<BODY>
 <H1>Simple Echo of variables with PHP</H1>

<?php

 $a = 10;
 $nom = "Patrick Ott";
 $somme = 123.456;

echo "Le nommé $nom a $somme francs dans la poche, mais il voudrait $a fois plus.";
?>

<p><hr>
</BODY>

echo an “instruction” to display a string (chain of characters)

Note: all the $xxx are replaced by their contents !

Simple arrays

Arrays are a sort of list (several values within the same variable)

Method 1:

$numbers[] =1;
$numbers[] =2;
$numbers[] =3;
$numbers[] =4;

Method 2:

$numbers = array (1, 2, 3, 4);
$names = array ("Pat", "Dave", "Surf", "K");

Simple arrays usage

$array[index]

Index starts at 0 ! (zero)

echo "Second element of $names is: $names[1];

Simple variables and some HTML generation

See: /guides/php/examples/simple/simple-arrays.php

<?php

// Some simple HTML
echo"<h1>Simple arrays</h1>";

$utilisateur = "cher étudiant";
$no_utilisateur = 3;

$numbers = array (1, 2, 3, 4);
$names = array ("Pat", "Dave", "Surf", "K");
$names[] = "Zorro";

// Note html <br> tag
echo "Salut $utilisateur. Vous êtes le numéro $no_utilisateur.<br>";

// echo with concatenation, use it to print complex things
echo "La quatrième personne s’appelle " . $names[3] ." ";

// simple echo
echo "et la cinquième personne s’appelle $names[4].<p>";
$n = sizeof($numbers);

// note that we have to use \ in order to print a $ !
echo "We have $n numbers in array \$numbers.";
?>

Associative arrays and multi-dimensional tables

$fruits = array(
    "fruits"  => array("a"=>"orange","b"=>"banana","c"=>"apple"),
    "numbers" => array(1, 2, 3, 4, 5, 6)
    "holes"   => array("first", 5 => "second", "third")
);

Summary - variables

You should, but don’t need to initialize varibales

$a = 1234; # decimal number
$a = -123; # a negative number
$a = 1.234; $a = 1.2e3; # floating point number
$str = "This is a string"; # string
$a[0] = "abc"; # element zero of un array
$a[1] = "def"; # element 1 of an array
$b["foo"] = 13; # element "foo" of an array

Constants.

Constants are "variables" with information that cannot change.

Do not use "$".

By convention, use capital letters.

Definition

define(<NAME>, <value>);

define("PI", 3.14);
define("REMERCIEMENTS", "Thanx for using our program<br>");
define("SALUTATIONS", "Je vous prie d’agréer, Madame, Monsieur, l’expression de nos sentiments dévoués");
$radius = 12;
$perimeter = 2 * $radius * PI;
echo REMERCIEMENTS;
echo "le périmètre du cercle is de " . $perimeter . "<br>";
echo SALUTATIONS;

result:

Thanx for using our program
le périmètre du cercle is de 77.76
Je vous prie d’agréer, Madame, Monsieur, l’expression de nos sentiments dévoués.

Simple expressions and operators

Arithmetic operators

Like normal math:

example	name	Returns the result:
$a +$b	Addition	Sum of $a and $b
$a - $b	Subtraction	$b minus $a
$a * $b	Multiplication
$a / $b	Division
$a % $b	Modulo	Rest of integer division $a by $b

Simple arithmetic

Application	: /guides/php/examples/simple/simple-calcul.php
Source	: /guides/php/examples/simple/simple-calcul.phps
To copy	: /guides/php/examples/simple/simple-calcul.text

$leisure_satisfaction = 5;
$work_satisfaction = 7;
$family_satisfaction = 8;
$index = ($leisure_satisfaction + $work_satisfaction + $family_satisfaction)
         / 3 ;
echo "<p align=center> Satisfaction Index = $index <b>";

assignment + addition in one step:

// sets $a to 8, as if we had said: $a = $a + 5;
$a += 5;

Operators for strings

concatenation of strings

Use the "." operator

example:

$a = "Hello ";
$b = $a . "World!"; // now $b = "Hello World!"

Note: There are dozens of string manipulation functions in PHP !!

assignment + concatenation in one step

$b = "Hello ";
 // sets $b to "Hello There!", just like $b = $b . "There!";
$b .= "There!";

Logical operators

example	name	result
$a and $b	"and"	result true, if $a et $b are true
$a && $b	"and"	"
$a or $b	"or"	result true, if $a or $b or both are true
$a	$b	"or"	"
$a xor $b	Or exclusive	result true, if $a or $b are true, but not both
! $a	"not"	result true, if $a is false(

comparison

example	name	result
$a == $b	equal	True if $a is equal to $b.
$a===$b	identical	True if $a==$b and same type (php 4.x)
$a != $b	different	True if $a is not equal to $b.
$a!==$b	not identical	True if $a!=$b or not same type (php4.x)
$a < $b	inferior	True if $a is strictly less than $b.
$a > $b	superior	True if $a is strictly greater than $b.
$a <= $b	inferior or equal	True if $a is less than or equal to $b.
$a >= $b	superior or equal	True if $a is greater than or equal to $b

You can use parenthesis if you like to group operators !

Simple comparisons

[/guides/php/examples/simple/simple-compare.php /guides/php/examples/simple/simple-compare.php]

[/guides/php/examples/simple/simple-compare.phps /guides/php/examples/simple/simple-compare.phps]

Note: in PHP each number equal or small than 0 is FALSE, each superior is TRUE

$a = "Migros";
$b = "Coop";
$result = $a==$b;
$result2 = $a > $b;
$result3 = $result==TRUE;
echo "Result One = $result. Result TWO = $result2. Result THREE = $result3.";

Selection (Conditions and tests)

Principle (several typical situations):

If a condition is true then do ...

If a condition is true then do ... , else do .....

If a condition is true then do ... , else if an other condition is true do ... , else ......

"IF" (several variants)

if (expr) statements

if (expr) statements else statements

if (expr) statements elseif (expr) statements else ...

if (expr) statements elseif (expr) statements [ elseif (expr) ... ]

expr = Expression must return TRUE or FALSE

statements = simple instructions or a block or instructions

simple: $a = 10;

block: { $a =12; echo "salut"; ..... }

Execution model

If expression = TRUE then execute statement(s)

If expression = FALSE then go to the next clause

Simple "if" (comparison)

/guides/php/examples/simple/simple-if.php

/guides/php/examples/simple/simple-if.phps (source)

Compares two numbers: $a and $b, and displays a message.

Here is a decision tree.

Simple decision tree

[[Image:]]

<?php

$a = 10; $b = 11;
print "a was $a, b was $b. ";
if ($a > $b) {
    print "a is bigger than b";
} elseif ($a == $b) {
    print "a is equal to b";
} else {
    print "==> a is smaller than b.";
}

?>

See also the following:

switch

foreach

do ... while

break and continue

PHP functions

Like all programming languages PHP allows to define procedures/functions.

A function is a a mini program that has a name and that you can "call" (invoke).

"Hey, take these informations, do something and (maybe) return the result"

Usually, you find function definition in the beginning of program (or within include files)

[[Image:]]

Color mixing for paint

http://tecfa.unige.ch/guides/php/examples/simple/ (files color-mix.*)

function color_mix($color1,$color2) {
  $result= "unknown";

  if ($color1 == "bleu" and $color2 == "rouge") {
    $result = "violet";   }
  elseif ($color1 == "jaune" and $color2 == "bleu") {
    $result = "green";  }
  elseif ($color1 == "noire" and $color2 == "blanc") {
    $result = "gris";  }
  else {
    $result = "orange";   }
  return $result;
}

// Two calls to this function, results saved in variables

$situation1 =  color_mix ("bleu", "rouge") ;

$situation2 =  color_mix ("jaune", "bleu") ;

// Print

echo "Bleu  et rouge donne $situation1 <br>";
echo "Jaune et bleu  donne $situation2";

HTML generation with functions

/guides/php/examples/simple/function-demo.php

/guides/php/examples/simple/function-demo.phps

<?php

// html formats a data element
function pretty_print ($output) {
    separator ();
    echo "<p align='center'> <strong>ELEMENT:</strong> $output </p>";
}
// outputs a separator
function separator () {
    echo "<hr size=4 width=70%>";
}
// data we have
$el1 = "Un arbre jaune";
$el2 = "Ein gelber Hund";
$el3 = "A yellow sky";
// dump the data
pretty_print($el1);
pretty_print($el2);
pretty_print($el3);

separator ();
echo "<hr>";
?>

Loops (iterations)

The "for loop" syntax

FOR (expr1; expr2; expr3) statement

expr1 is evaluated at start

expr2 is evaluated at start of each loop,if result = TRUE the loop will continue, else it will stop

expr3 is evaluated at the end of each loop,

statement is executed for each loop.

Love generation

see: /guides/php/examples/html-generate/love.php

see: /guides/php/examples/html-generate/love.phps

for ($i=1; $i<=10; $i++) {
    print "I love you so ! "; }

result:love you so ! I love you so ! I love you so ! I love you so ! I love you so ! I love you so ! ......

echo "Je t’aime plus que toi.<br>
for ($i=2; $i<=10; $i++) {
    echo "Non, je t’aime $i fois plus que  toi ! ";
}

result:

Je t’aime plus que moi.
Non, je t’aime 2 fois plus que moi ! Non, je t’aime 3 fois plus que moi ! Non, je t’aime 4 fois plus que moi ! Non, je t’aime 5 fois plus que moi ! Non, je t’aime 6 .....

Other PHP elements:

$i is used as so-called iteration variable. At start $i = 1 or 2.

echo

print works like print.

Generation of html tables

see: /guides/php/examples/html-generate/love.php

see: /guides/php/examples/html-generate/love.phps

see: /guides/php/examples/html-generate/love.text

$love_list = array ("a lot", "a bit", "somewhat", "à mourir", "forever", "until notice", "more than I love my dog");
<table border align="center">
<?
// define a function to generate a table
function build_table($list) {
 for ($i=0; $i < sizeof($list); $i++) {
   $love_text = $list[$i];
   echo "<tr> <td> ... I love you</td> <td>$love_text</td>";
   }
}
// call the function, generate the table
build_table($love_list);
?>
</table>

Note:

PHP is used with the HTML <table> element

The build_table function is called with an array

There exist more looping constructs in PHP (like while or for-each) !

Practical advice

Debugging

Look at the generated HTML code "View Source")

Insert this in you PHP file (will give you lots of information !)

phpinfo();

Insert print statements!

echo "DEBUG: \$var = $var";
echo "TEST: var = $var";

Raise "error reporting" to its maximum !!!

Insert this on top:

error_reporting(E_ALL);

Portals

Warning: NEVER insert blank lines at start or end of a file !!

Most files should stop like this (no line feed !!) ?>

... because PHP starts producing HMTL headers as soon as it sees a little blank space before or after php code <?php .... ?>

HTML forms processing with PHP

Forms processing with PHP I (Calcul)

Simple quiz and POST to a php file

See: /guides/php/examples/simple-calculate/formulaire.html

Source: /guides/php/examples/simple-calculate/formulaire.text

This example shows:

how to treat and HTML form

how to compute and display a result.

[[Image:]]

Part of the HTML form:

<form action="calcul.php" method="post">

Quelles sont vos connaissances de HTML ?
<input type="radio" name="choice" value="1" checked>faibles
<input type="radio" name="choice" value="2">moyennes
<input type="radio" name="choice" value="3">bonnes
<br>
Indiquez votre expertise en programmation:
<input type="radio" name="choice2" value="1" checked>absente
<input type="radio" name="choice2" value="2">moyenne
<input type="radio" name="choice2" value="3">bonne
<P>
<input type="submit" value="Voir le result!">
</form>

[[Image:]]

Retrieve values of an HTML form

Data from a from a stored by the server in a so-called super global variables

Use $_POST to deal with POST variables

POST: values are handed over attached (and not visible) to the server

Use $_GET for GET variables

GET: values are handed over in the URL string (user can see these)

You can use the "name" attribute of the form to retrieve values

In our example, we use $_POST:

$choice = $_POST[’choice’];
$choice2 = $_POST[’choice2’];

In our example, we will use two PHP variables:$choice and $choice2

Computing and display of results

see: /guides/php/examples/simple-calculate/calcul.phps

we add result of the two values and compute a result with an if clause.

<?php

// Get values from the form
$choice = $_POST[’choice’];
$choice2 = $_POST[’choice2’];

// Compute score
$score = $choice + $choice2;

// Compute message as function of result
echo "<h3>Votre score is de " . $score . "</h3>";
if ($score < 3) {
  echo "<p>Vous êtes un débutant</p>";
} elseif ($score < 5) {
  echo "<p>Vous avez un niveau moyen</p>";
} else {
  echo "<p>Vous êtes un expert !</p>";
}
?>

Inhibit direct access to PHP (without data)

(1) if (isset($_POST[’choice’])) then { ..... } else { echo "sorry ......."; }

(2) Alternative: if (!isset($_POST[’choice’])) {echo "sorry"; exit; }

Forms processing with PHP II

Checkboxes with PHP - arrays

/guides/php/examples/simple-calculate/formulaire4.text

/guides/php/examples/simple-calculate/formulaire4.html

Part of the HTML code:

<form action="calcul4.php" method=post>
Quels sont vos couleurs préféres?
<br>
<input type="checkbox" name="choice[]" value="Red">Red
<table bgcolor="red" width="50"><tr><td> </td></tr></table>

<input type="checkbox" name="choice[]" value="Blue">Blue
<table bgcolor="blue" width="50"><tr><td> </td></tr></table>

<input type="checkbox" name="choice[]" value="Green">Green
<table bgcolor="green" width="50"><tr><td> </td></tr></table>
.....
<input type="checkbox" name="choice[]" value="Black">Black
<table bgcolor="black" width="50"><tr><td> </td></tr></table>

<input type="submit" value="Voir le result!">
</form>

Remember the syntax to put all values into an array: "choice[]"

PHP code:

<?php
$choice = $_POST[’choice’];

echo("<h3>Vos couleurs préférées sont </h3>");

for ($i=0;$i<sizeof($choice);$i++) {
    if (isset($choice[$i])) {
       echo("$choice[$i] - ");
    }
}
?>

All in one solution ?

You can put both the form and the processing code in a single page

In this case, test if the file is called with data from a form, see $process below

<? 
if (!isset($_POST[’process’])) {
?>
//... lets display the form)

  <FORM METHOD="POST" ACTION="<? echo $PHP_SELF ?>">
  .....
  </FORM>

<?
} else {
//... we got data, so let’s process
}
?>

Polishing: Test if we have all the POST/GET variables

2 methods to test what we have in $_POST or $_GET

"array_key_exists()"

if (array_key_exists(’first’, $_POST)) { .... do something ...};

"isset()" to see if a variable exists:

if (isset($POST[’first’]) ) { .... do ....}

The difference is that

array_key_exists returns TRUE if value is NULL

isset returns FALSE if value is NULL.

ATTENTION, to test <input type="text"> you also may want to test if there is an empty string.

“empty()”

to decide if user filled in a text field

if (empty ($input) ) { ... complain ... } else { ... do ...}

empty() returns TRUE if a value is: "", 0, "0", NULL, FALSE, array(), ....

Session management

PHP has session support (can keep variables over a whole user session).

Each visitor gets an identifier (a "sessions id"). It is stored in a cookie (in the www client) or within the URL.

This information is available in super global: $_SESSION

Restrict repetitive access to a page

http://tecfa.unige.ch/guides/php/examples/sessions/

session_start();
if (!isset($_SESSION[’count’])) {
    $_SESSION[’count’] = 0;
} else {
    $_SESSION[’count’]++;
}
if ($_SESSION[’count’] > 2) {
echo ’<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">’;
    echo "<html> <body>";
    echo "Sorry it’s over you can’t do it twice";
    echo "</body> </html>";
    exit;
  } 
// .... continue code with access time = 1 and 2

On-line surveys and file-based storage

Survey

see: http://tecfa.unige.ch/guides/php/examples/form-file-demo/

new-entry.php contains the form and code

dump_results.php shows file contents

The HTML form

This time we use PHP to generate the HTML code

$scales = array("food", "work", "love", "leisure", "sports");
function scale ($thing) {
   echo "<TR> <TD align=right>Importance of <STRONG>$thing</STRONG>:</TD>";
   echo "<TD><select name=$thing>";
   echo "<option value=1>1 - totally unimportant";
   echo "<option value=2>2 - not important";
   echo "<option value=3 selected>3 - rather not important";
   echo "<option value=4>4 - slightly important";
   echo "<option value=5>5 - rather important";
   echo "<option value=6>6 - very important";
   echo "</select>";
   echo "</TD></TR>";
   }

function dump_scales ()  {
 global $scales;
 reset($scales);
 do {
    $scale = scale(current($scales));
    echo "$scale\n";
    }
    while (next($scales));
 } ?>
<form> <table>
......
dump_scales();
......
</table> </form>
Ecrire dans un fichier
// check existance of file (or try to create it)
  // a better alternative to touch() would be is_file, is_writable and so on.
    $try = touch($file_name);
  if (!$try) {
    echo "<p>Sorry I can’t open a file, something is wrong";
    exit;
  }

  // this is the stuff we get from the form, we insert it into an array
    $input = array ($login, $password, $fullname, $url, $food, $work, $love, $leisure, $sports);
  
  // so we can make a big string with tabs between the elements
    // note that we add a \n (line break) to the end of the string.
    $output_line = implode ($input,     "                            ")."\n";

  // Now open the file (get a file pointer)
    // We will append to it and therefore use the "a" option
    $output_stream = fopen($file_name, "a");
  // and dump the string into the file
    $result = fputs ($output_stream, $output_line);
  
  // give feedback
    if ($result) {
      echo "<p>Your data have successfully been registered.";
    }
  else {
    echo "<p>Too bad, the db did not want your data.";
  }
  // close the file pointer
    fclose($output_stream);
  ?>

<?
  // EXIT here ... we don’t want to see the form again. If you do, kill the exit
  exit;
}
?>

Remember

fopn (<file name>, "a")

to open a file and then append.

fputs(<handle>, “string”)

to write to a file

WARNING: This will attract spammers !!

Dump contents of a file

.... we just insert it a <pre> with an “include”

<BODY>
    <H1>PHP/MySQL Demo - Dump Database Contents</H1>

<? 
  /* Daniel.Schneider@tecfa.unige.ch
  Will dump the contents of the results file
  */
?>

  <strong>Results registered so far:</strong>
<pre>
<? readfile("results/result.text"); ?>
</pre>
..........

</BODY>

Important:

Use "readfile", and not "include" or "require", else you will get hacked !!

Other formats than HTML

Principle: in the FIRST line of your program you have to define the content-type:

example: Header("Content-type: image/gif");

Example XML

Header("Content-type: text/xml);

Example SVG

Header("Content-type: image/svg+xml");

Example RDF

Header("Content-type: application/rdf+xml");

Generate some simple XML

http://tecfa.unige.ch/guides/php/examples/simple/simple-calcul-xml.php

http://tecfa.unige.ch/guides/php/examples/simple/simple-calcul-xml.phps

http://tecfa.unige.ch/guides/php/examples/simple/simple-calcul-xml.css

<?php
header("Content-type: text/xml");
print(’<?xml version="1.0" encoding="iso-8859-1"?>’ . "\n");
print(’<?xml-stylesheet href="simple-calcul-xml.css" type="text/css" ?>’);

$leisure_satisfaction = 5; $work_satisfaction = 7;  $family_satisfaction = 8;
$index = ($leisure_satisfaction + $work_satisfaction + $family_satisfaction) / 3 ;
echo "<resultat> Satisfaction Index = $index </resultat>";
?>

PHP tutorial - basics: Difference between revisions

Revision as of 18:24, 9 February 2010

Introduction

The programming language PHP

Elements of programming

Navigation menu

Slow Search