Archive:PHP and MySQL Programming/Syntax Overview

2008-09-23T11:15:49Z

122.167.157.25: /* PHP tags: */

== PHP tags: ==

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

* Enclose php code

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

* Embedded in normal HTML code

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

Example:

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

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

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

Example:

<source lang="php">
<?php
$name = "Bobby";
?>

<?=$name?>
</source>

Which will output ''Bobby''.

Example:

<source lang="php">
<?=date("Y-m-d H:i:s")?>
</source>

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

== Commenting ==

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

* Comments out one line

* Example:
<source lang="php">
echo "Hello"; # Everything from the hash is commented out
</source>

* Example:
<source lang="php">
# This entire line is commented out
</source>

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

* Works just as in Java and JavaScript

* Same function as '''#'''

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

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

* Example:
<source lang="php">
/*All of this is
commented out.
Even this line!*/
</source>

== Variables ==

➢ Variables in PHP are denoted by the $ prefix.

* Example:
<source lang="php">
$a = “Hello World”; # this assigns the string “Hello World” to $a.
$b = “$a, I'm Ralfe”; # this assigns “Hello World, I'm Ralfe” to $b.
$b = $a.”, I'm Ralfe”; # exactly the same as the previous example.
</source>

➢ PHP supports dynamic variables.

* Example:
<source lang="php">
$c = “response”;

$$c = “Hello Ralfe”; # this assigns “Hello Ralfe” to $response.
</source>

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

* Example:
<source lang="php">
$a = 4;

$b = 12;

print “The value of a is $a.”; # Uses a as a String.

$c = $a + $b; # $a is now used as an Integer again.
</source>

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

Example:
<source lang="php">
$a = true;

$b = 1; # $a and $b are the same thing!

$c = false;

$d = 0; # $c and $d are the same thing!
</source>

== Operators ==

➢ Arithmetic Operators

* Example:
<source lang="php">
$a = 4;

$b = 2;

$a + $b = 6; // Addition

$a - $b = 2; // Subtraction

$a * $b = 8; // Multiplication

$a / $b = 2; // Division

$a % $b = 0; // Modulus

$a++; // Increment

$a--; // Decrement
</source>

➢ Assignment Operators

* Example:
<source lang="php">
$a = 4;

$b = $a;

// $b = 4;
</source>

➢ Comparison Operators

* Example:
<source lang="php">
$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
</source>

== Concatenation ==

* Example:
<source lang="php">
$a = "Fill the halls ";

$b = "with poisoned ivy...";

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

// $c = "Fill the halls with poisoned ivy...";
</source>

== Arrays ==

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

* Example:
<source lang="php">
$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;
</source>

== Decision and Loop Statements ==

'''IF THEN ELSE statement'''

* Example:
<source lang="php">
$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
</source>

'''SWITCH statement'''

* Example:
<source lang="php">
$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
</source>

'''FOR statement'''

* Example:
<source lang="php">
for ($i = 0; $i < 10; $i++) {
# initialize $i ; while condition ; increment statement
echo $i;
}

// OUTPUT:
// 0123456789
</source>

'''FOREACH statement'''

* Example:
<source lang="php">
$a = array(1, 2, 3, 4, 5);

foreach ($a as $val){
echo $val;
}

// OUTPUT:
// 12345
</source>

'''WHILE statement'''

* Example:
<source lang="php">
while ($row = mysql_fetch_row($result)){
print $row[0];
}
</source>

'''DO WHILE statement'''

* Example:
<source lang="php">
$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!
</source>

== Functions ==

* Example:
<source lang="php">
function square_number($number) {
return ($number * $number);
}

$answer = square_number(10);
echo "The answer is {$answer}";

// OUTPUT:
// The answer is 100
</source>

== Classes ==

* Example:
<source lang="php">
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
</source>

[[../Introduction to PHP/|Previous: Introduction to PHP]] | [[../|TOC]] | [[../File Handling/|Next: File Handling]]

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