411 REFERENCE · Wikibooks
PHP and MySQL Programming/PHP Syntax
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
PHP tags:
<?php [code] ?>
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:
<?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
$name = "Bobby";
?>
<?=$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 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;
# 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 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