Archive:PHP and MySQL Programming/PHP Syntax

2006-08-07T12:26:19Z

59.144.154.75: /* '''<?=''' */

[[Programming:PHP and MySQL|<< Back to PHP and MySQL]]

== PHP tags: ==

=== '''<?php [code] ?>''' ===

* Enclose php code

* Can be configured in the php.ini to be <? ?>, <script language="php"> </script> etc.

* Embedded in normal HTML code

* Within php tags, statements are separated by a ; (generally also followed by a new line).

Example:

<?php
print “Hello World\n”;
$date = date(“Y-m-d H:i:s”);
print “The date and time at the moment is $date”;
?>

=== '''<?=''' ===

* Used if you just want to print out the value of a variable

Example:
<?php
$name = "Bobby";
?>

<?echo $name?>
Which will output ''Bobby''.

Example:
<?=date(“Y-m-d H:i:s”)?>

Which will output something like ''2005-11-09 19:40:05''.

== Commenting ==

==='''#'''===

* Comments out one line

* Example:
echo “Hello”; # Everything from the hash is commented out

* Example:
# This entire line is commented out

==='''//'''===

* Works just as in Java and JavaScript

* Same function as '''#'''

==='''/* (text) */'''===

* Comments out everything between the /* and the */

* Example:
/*All of this is
commented out.
Even this line!*/

== Variables ==

➢ Variables in PHP are denoted by the $ prefix.

e.g. : $a = “Hello World”; # this assigns the string “Hello World” to $a.

e.g. : $b = “$a, I'm Ralfe”; # this assigns “Hello World, I'm Ralfe” to $b.

e.g. : $b = $a.”, I'm Ralfe”; # exactly the same as the previous example.

➢ PHP supports dynamic variables.

e.g. : $c = “response”;

e.g. : $$c = “Hello Ralfe”; # this assigns “Hello Ralfe” to $response.

➢ PHP variables do not have to be declared ahead of time, nor do they require a type
definition. PHP handles all data type conversions.

e.g. : $a = 4;

e.g. : $b = 12;

e.g. : print “The value of a if $a.”; # Uses a as a String.

e.g. : $c = $a + $b; # $a is now used as an Integer again.

➢ PHP supports boolean variables, which can be assigned either a one or a zero, or a
true or false.

e.g. : $a = true;

e.g. : $b = 1;

e.g. : # $a and $b are the same thing!

e.g. : $c = false;

e.g. : $d = 0;

e.g. : # $c and $d are the same thing!

== Operators ==

➢ Arithmetic Operators

$a = 4;

$b = 2;

// Addition: $a + $b = 6

// Subtraction: $a - $b = 2

// Multiplication: $a * $b = 8

// Division: $a / $b = 2

// Modulus: $a % $b = 0

// Increment: $a++

// Decrement: $a--

➢ Assignment Operators

$a = 4;

$b = $a;

// $b = 4;

➢ Comparison Operators

$a == $b // test if two values are equal

$a != $b // test if two values are not equal

$a < $b // test if the first value is less than the second

$a > $b // test if the first value is greater than the second

$a <= $b // test if the first value is less than or equal to the second

$a >= $b // test if the first value is greater than or equal to the second

== Concatenation ==

$a = “Fill the halls “;

$b = “with poisoned ivy...“;

$c = $a . $b; # the '.' operator concatenates two variables.

// $c = “Fill the halls with poisoned ivy...”

== Arrays ==

PHP supports both numerically indexed arrays as well as associative arrays.

$a = array(1, 2, 3, 4);

// $a[0] = 1;

// $a[1] = 2;

// $a[2] = 3;

// $a[3] = 4;

$b = array(“name” => ”Fred”, “age” => 30);

// $b['name'] = “Fred”;

// $b['age'] = 30;

== Decision and Loop Statements ==

'''IF THEN ELSE statement'''

$a = 1;
$b = 10;
if ($a > $b) {
echo “a is greater than b”;
}
else if ($a == $b){
echo “a is equal to b”;
}
else{
echo “a is not greater than b”;
}

'''SWITCH statement'''

$a = 100;
switch($a){
case(10):
echo “The value is 10”;
break;
case(100):
echo “The value is 100”;
break;
case(1000):
echo “The value is 1000”;
break;
default:
echo “Are you sure you entered in a valid number?”;
}

'''FOR statement'''

$a = 10;
for ($i = 0; $i < 10; $i++){
# initialize $i ; while condition ; increment statement
print “$i”;
}

'''FOREACH statement'''

$a = array(1, 2, 3, 4, 5);
foreach ($a as $val){
echo “$val”;
}

'''WHILE statement'''

while ($row = mysql_fetch_row($result)){
print $row[0];
}

'''DO WHILE statement'''

$i = 0;
# Note that it might seem that $i will
do{
# never be printed to the screen, but
print $i;
# a DO WHILE loop always executes at
} while ($i >0);
# least once!

== FUNCTIONS ==

function my_function($value){
if (!$value){
return 0;
}
else{
return ($value % 2);
}
}
$a = 45;
$ans = my_function($a);

== Classes ==

class my_class {
var $value1;
var $value2;
function set_value1($val){
$this->value1 = $val;
}
function set_value2($val){
if ($this->value1 > 0){
$this->value2 = $val;
}
else{
$this->value2 = 0;
}
}
}
$new_class = &new my_class;
$new_class->set_value1(10);
$new_class->set_value2(2);

[[Programming:PHP and MySQL:Introduction|<< 1. Introduction]] | [[Programming:PHP and MySQL|TOC]] | [[Programming:PHP and MySQL:File Handling|>> 3. File Handling]]

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