PHP tutorial - basics

The educational technology and digital learning wiki
Jump to navigation Jump to search


Learning goals
  • Be able to make modifications in a PHP file (in particular configuration files)
Moving on
Level and target population
  • Beginners
  • This is a first version made from slides. Lot's of missing prose - Daniel K. Schneider 19:24, 9 February 2010 (UTC).
  • Warning: There may be mistakes in the code that you can copy/paste. Slides to wiki translation isn't working very well and needs manual fixing. Try using the associated files instead.

PHP standards for Hypertext Preprocessor


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.


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.)


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


PHP features


Free and open source (GPL)
cross-platform (Unix, Linux, BSD, MacOS X, Win32, etc.)


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


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 ..... ?>

For example:

 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).


inserts content of file when this expression is evaluated

include ("file name");


inserts content of file when the php file is loaded

require ("file name");

Variant (recommended):

include_once() and require_once().

Only include once, will make your application faster.

File inclusion example
     <TITLE>Simple Include Demo (21-Apr-1998)</TITLE>
 <?php include("style.text"); ?>
     <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>.
       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>
       <LI> bullet item </LI>
       <LI> bullet item </LI>
 /* A footer */

Elements of programming

Program= algorithm + data structures
Programming elements

PHP syntax overview:

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

Each instruction is ended with a ";"
Comments // or #, or included within /* ... */

Variables, data structures and assignments

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: =


$variable = "content" ;


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

Using variables with content strings example:

/guides/php/examples/simple/simple-echo.php (application)
/guides/php/examples/simple/simple-echo.phps (pretty source)
/guides/php/examples/simple/simple-echo.text (source)
  <H1>Simple Echo of variables with PHP</H1>

  $a = 10;
  $nom = "Patrick Ott";
  $somme = 123.456;
  echo "Le nommé $nom a $somme francs dans la poche, mais il voudrait $a fois plus.";
echo is 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 lists (several values within the same variable)

Array creation - method 1:

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

Array creation - method 2:

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

Use of simple arrays:


Index starts at 0 ! (zero). Example:

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

Example: Simple variables and some HTML generation

 // 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 are "variables" with information that cannot change.

By convention, use capital letters.
define(<NAME>, <value>);
Do not use "$".


 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 "le périmètre du cercle is de " . $perimeter . "<br>";


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 ...

Returns the result:
$a +$b
Sum of $a and $b
$a - $b
$b minus $a
$a * $b
$a / $b
$a % $b
Rest of integer division $a by $b


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

For concatenation of strings use the "." operator


 $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

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


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

Some simple comparisons:

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.";


(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" example (comparison)

simple-if.phps (source)

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

Simple decision tree
 $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 contructs:

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).

Principle: "Hey, take that information, do something and (maybe) return the result"

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


Color mixing for paint example (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 example:

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

Love generation example:

/guides/php/examples/html-generate/love.php (program)
/guides/php/examples/html-generate/love.phps (source)
 for ($i=1; $i<=10; $i++) {
     print "I love you so ! "; }


I love you so ! I love you so ! I love you so ! I love you so ! I love you so ! I love you so ! ......

Here is a slightly more complex one:

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


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:

print works like print.

Generation of html tables example

 $love_list = array ("a lot", "a bit", "somewhat", "à mourir", "forever", "until notice", "more than I love my dog");
 <table border align="center">
 // define a function to generate a table
 function build_table($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


PHP is used within 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


(1) Look at the generated HTML code "View Source")

(2) Insert phpinfo() in your PHP file (will give you lots of information, e.g. about PHP installation, its environment, variables passed to script from the server, etc.)


(3) Insert print statements!

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

(4) Raise "error reporting" to its maximum ! Insert this on top:


(5) Know where your server / php log files are

In some configurations, php error messages and notices are not displayed on the rendered web page. You will have to find these in the log files or the server. Check the settings of the php.ini file to find out.

(6) 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

Simple quiz and POST to a php file

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

This example shows:

  • how to treat and HTML form
  • how to compute and display a result.
HTML form and a php script

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


Retrieve values of an HTML form

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

Use $_POST to deal with POST variables

POST: values are attached to the HTML request (and not visible to the user)

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'];

We now have two PHP variables: $choice and $choice2

Computing and display of results


We add the the two values and compute a summary result with an if clause.

 // 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 &ecirc;tes un d&eacute;butant</p>";
 } elseif ($score < 5) {
   echo "<p>Vous avez un niveau moyen</p>";
 } else {
   echo "<p>Vous &ecirc;tes 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)


Part of the HTML code:

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

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

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

 <input type="submit" value="Voir le result!">
Remember the syntax to put all values into an array: "choice[]"

PHP code:

 $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 php page. In this case, test if the file is called with data from a form or through a link/a navigator. See the variable$process below

 if (!isset($_POST['process'])) {
 //... lets display the form)

 } else {'''
 //... we got data, so let’s process


To test if we have all the POST/GET variables, we may use two methods to see what we have in $_POST or $_GET:

 if (array_key_exists('first', $_POST)) { .... do something ...};
to see if a variable exists:
 if (isset($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.

to decide if the 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 example:
 if (!isset($_SESSION['count'])) {
     $_SESSION['count'] = 0;
 } else {
 if ($_SESSION['count'] > 2) {
 echo '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">';
     echo "<html> <body>";
     echo "Sorry it's over you can't do it twice";
     echo "</body> </html>";
 // .... continue code with access time = 1 and 2

On-line surveys and file-based storage

This is a simple code that shows how to collect survey data.
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;
  do {
     $scale = scale(current($scales));
     echo "$scale\n";
     while (next($scales));
  } ?>
 <form> <table>
 </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";
   // 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
   // EXIT here ... we don't want to see the form again. If you do, kill the exit


 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

 with an “include”

<source lang="html4strict">
     <H1>PHP/MySQL Demo - Dump Database Contents</H1>
   Will dump the contents of the results file
   <strong>Results registered so far:</strong>
 <? readfile("results/result.text"); ?>




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

Other formats than HTML

PHP supports any other format. By default a PHP script starts creating an HTML script as soon as it encounters and HTML section or an echo/print/etc. instruction.

Principle: Before any other output in your program, you have to define the content-type (e.g. put this into the first line).

Example binary pictures

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 example
 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>";