PHP Workshop Notes

PHP A scripting language design to produce HTML pages

PHP Introduction
PHP serves the same purpose as Java Server Pages (JSP) and Active Server Pages (ASP)
All are server-side languages “parsed” by a web server
Script execution results are sent to a browser as an HTML page
PHP is a type-less language

PHP Structure
Tradition: Start with an HTML file
Add special tags to separate PHP code from HTML statements
Web server parses the PHP file, producing HTML
Now can be used to output XML, image, PDF, just by setting content-type

Example: myfirst.php
<html>
<body>
<?php
//A comment
/*Or comment like this*/
print("Hello world");
$v = 5;
print("Hello again " . $v );
print("Hello a third time $v");
?>
</body>
</html>

Variables
All variables start with a dollar sign, $
$u = 5;
$v = “hello”;
$w = 1.22;
$x = $u + $v; //arithmetic with + - ONLY
$y = $v . $v; //concatenation with period operator
$x = $u . $u; //produces 55, not 10

Printing
$u = 5;
print( “5 hello” ); //print anything in quotes
print( $u . “hello” ); //prints 5hello
print( “$u Hello” ); //prints 5 Hello

String-Related Functions
$v = “hello”;
strlen( $v); //returns 5
trim( $v); //trims any spaces on either side of a string
$x = strtolower ($v); //$x has hello
$x = strtoupper($v); //$x has HELLO
$str = “abcdef”;
$a = substr( $str, 3, 3 );
# of characters to copy Start position, zero indexed Source string “ def” Can be negative to start from right side

Getting HTML Form Data
There are 3 ways to get form data in PHP
Global variables – this is a bad way because of security problems. PHP creates a variable with a name matching the form field name in the source HTML.
POST variable associative array
Prior to version 4.1, $HTTP_POST_VARS
4.1 and after, $_POST
GET variable associative array
Same as POST, but use GET

Examples
Global variables (HTML has field with name ‘abc’)
print ($abc);
POST
print($_POST(‘abc’)); //4.1 and after
GET
print($_GET(‘abc’)); //4.1 and after

Comparing Strings
strcmp( $a, $b ); //works like C function
Returns:
– 1 if first string less than second string
0 if the same
1 if first string greater than second string
It is case sensitive

PHP Syntax Similarities
Has a switch statement
for loop is the same, but uses PHP variable syntax
for ($i=0; $i < 10; $i++ ){ …. }
while and if are also what you’d expect
Standard logical operators: ==, &&, <, > …

Other Useful Functions
round ($a); //rounds a number
is_numeric($v); //returns true/false
rand($start, $end); //Produces int rand

Current Date/Time
Use date function to get the current date.
Takes a format string to provide the date in a format you want. See http://php.net/date .
Use time function to get the current time.
Returns the current time measured in the number of seconds since the Unix Epoch (January 1 1970 00:00:00 GMT).

Creating Functions
function myfunc( $a, $b, $c ) {
//this is my code
return $x;
}

External PHP Files
Can use require or include
Require will produce a fatal error if the file cannot be found
Include will just ignore a missing script file
require(‘my.php’);
include(‘my.php’);
The files can contain PHP and/or HTML

Arrays
Creating an array
$a = array(1,2,3,4,5);
Accessing array elements
$v = $a[2];
$a[2] = 5;
$a[] = 1; $a[] = 2; $a[] = 3; //appends to array

Iterating Over Arrays
for ($i=0; $i<count($a); $i++ ) {
print ($a[i]);
}
foreach( $a as $item ) {
print( “$item”);
}
Array variable Local variable. Set to next array element each iteration.

Other Array Functions
$m = max($a); //returns max value in array
$m = min($a); //returns min value in array
$s = array_sum($a); //returns sum or array values
sort($a); //sorts the items in the array. Changes
//the array itself
Optional second argument is “sort flags” to control the sort.

Associative Arrays
Arrays containing key/value pairs
$s = array( ‘a’=>’alpha’, ‘b’=>’beta’, … );
print ( $s[‘b’] );
The parameter to the left of => is the key.
The right parameter is the value.

SQL – Structured Query Language
A language for accessing relational databases
Relational databases have tables
Tables have fields and contain rows of data

SQL Syntax – SELECT
Used for retrieving data from a database
SELECT [fields] FROM [tables] WHERE [expr]
Examples
select * from users
select abc, def from mytable where ghi=5

SQL Syntax – INSERT
Used to insert new data in a table
INSERT INTO [table] [field names] VALUES [values]
Examples
insert into users (abc,def,ghi) values (‘111’,22,’cc)
insert into xyz values (1,2,3,4,5)

SQL Syntax – UPDATE
Updating one or more values in existing rows in a table
UPDATE [table] SET [name=value pairs] WHERE [expression]
Examples
update mytable set a=‘aaa’, b=55 where c=11

PHP and Mysql Database
5 steps
Connect to the Mysql DBMS
Pick a database
Execute an SQL statement
If the SQL was a ‘select’, retrieve the data
Close the connection

Connecting to Mysql DBMS
$con = mysql_connect( /* 3 arguments */ );
Your Mysql DBMS server process network location
Your Mysql user ID
Your Mysql user password
For tonight only,
mysql_connect(‘www.freesql.org’,’upeworkshop’,’upeworkshop’);

Selecting a Database
mysql_select_db( ‘upeworkshop’ );

Executing an SQL Statement
mysql_query( /*SQL statement*/ );
Proper form for any SQL not a Select
if ( !mysql_query ( “update a ….” ); ) {
echo mysql_error(); //for easy debugging, not for final user-oriented website
} //returns true/false if it worked, or not

For Select SQL Statements
$r = mysql_query( ‘select * from abc’ );
while ( $row = mysql_fetch_row( $r ) ) { … }
$row contains a row of data
returns false when no more rows available
Iterating through the fields in the row
foreach ( $row as $item ) { … }
OR access the fields using index position (zero indexed)
OR put results in an associative array – less error prone
while ($row = mysql_fetch_assoc($r)){
echo $row[‘firstname’];
}

Closing a Connection
mysql_close( $con );

PHP Workshop Notes

by Pamela Fox

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