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

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