Archive:PHP and MySQL Programming/PHP Syntax

PHP tags :

<??>

– Enclose php code

– Can be configured in the php.ini file to be anything (i.e. : <%%>)

– Embedded in normal HTML code

– Within php tags, statements are separated by ; .

– e.g. :

<?

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

– e.g. : <?= $name ?>

prints out bobby.

– e.g. : <?= date(“Y-m-d H:i:s”) ?>

prints out 2005-11-09 19:40:05.

Commenting

#

– Comments out one line – e.g. : echo “Hello”; # everything from the hash is commented out – e.g. : # This entire line is commented out

//

– Works just as in Java and JavaScript – Exactly the same as the #

/*....*/

– Comments out everything between the /* and the */ – e.g. : /*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

1. --- 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”; }

1. --- 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?”; }

1. --- FOR statement ---

$a = 10; for ($i = 0; $i < 10; $i++){

1. initialize $i ; while condition ; increment statement

print “$i”; } Page 4

1. --- FOREACH statement ---

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

1. --- WHILE statement ---

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

1. --- DO WHILE statement ---

$i = 0;

1. Note that it might seem that $i will

do{

1. never be printed to the screen, but

print $i;

1. a DO WHILE loop always executes at

} while ($i >0);

1. 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);