PHP and MySQL Programming/PHP Syntax



 * Enclose php code


 * Can be configured in the php.ini to be <? ?>, etc.


 * Embedded in normal HTML code


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

Example:



<?=

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

Example:  <?=$name?> Which will output Bobby.

Example: <?=date(“Y-m-d H:i:s”)?>

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

#

 * Comments out one line

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


 * Example:
 * 1) This entire line is commented out

//

 * Works just as in Java and JavaScript


 * Same function as #

/* (text) */

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

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

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 is $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"; } // OUTPUT: // 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?"; } // OUTPUT: // The value is 100

FOR statement

for ($i = 0; $i < 10; $i++) { # initialize $i ; while condition ; increment statement echo $i; } // OUTPUT: // 0123456789

FOREACH statement

$a = array(1, 2, 3, 4, 5); foreach ($a as $val){ echo $val; } // OUTPUT: // 12345

WHILE statement

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

DO WHILE statement

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

Functions
function square_number($number) { return ($number * $number); } $answer = square_number(10); echo "The answer is {$answer}"; // OUTPUT: // The answer is 100

Classes
class dog { var $name; function dog($name){ $this->name = $name; }   function bark{ echo "Woof! Woof!"; }   function who_am_i { echo "My name is {$this->name), and I am a dog";   } } $the_dog = new dog("John"); $the_dog->who_am_i; // OUTPUT: // My name is John, and I am a dog