PHP and MySQL Programming/PHP Syntax
PHP tags:
edit<?php [code] ?>
edit- 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”; ?>
<?=
edit- Used if you just want to print out the value of a variable
Example:
<?php $name = "Bobby"; ?> <?=$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
edit#
edit- Comments out one line
- Example:
echo “Hello”; # Everything from the hash is commented out
- Example:
# This entire line is commented out
//
edit- Works just as in Java and JavaScript
- Same function as #
/* (text) */
edit- Comments out everything between the /* and the */
- Example:
/*All of this is commented out. Even this line!*/
Variables
edit➢ 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
edit➢ 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 >= $b // test if the first value is greater than or equal to the second
Concatenation
edit$a = “Fill the halls “;
$b = “with poisoned ivy...“;
$c = $a . $b; # the '.' operator concatenates two variables.
// $c = “Fill the halls with poisoned ivy...”
Arrays
editPHP 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
editIF 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; # 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
editfunction square_number($number) { return ($number * $number); } $answer = square_number(10); echo "The answer is {$answer}"; // OUTPUT: // The answer is 100
Classes
editclass 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