Class Work
Get the examples programs to work
Homework
Use the file_exists function to test that the orders files exists in the page 67 version of
process order
Create an inventory file for use by processorder.php. Modify processorder.php so that it
updates the contents of the file every time processorder successfully carries out a
transaction. The inventory file will contain three lines – the first line is the number of
tires on hand, second line is the number of units of oil on hand; the third line is the
number of spark plugs on hand.
Modify the program so that the price of each product as well as the number of items of
the product are stored in the array.
Write a program that adds and removes produces from the inventory file. Write one
version of the program for an inventory file that contains no prices and one version for an
inventory file that contains prices
Chapter 2 Storing and Retrieving Data
Saving Data For Later
Why do you want to save data for later?
Processing Files
A sales transaction reads the order from the user, finds information about the item to be
sold from a database, and updates the data base to reflect the purchase
Opening a File
Opening a File connects your program to the Operating System’s file manager. The File
appears to the program as a File Name. The file manager uses the File Name to create a
resource about by means of which the program can get detailed information about the file
and view and modify the contents of the file
File Mode
A File Mode determines the operations that the program can apply to the file. See page
61. We will always open files as binary
The fopen function
$_SERVER[‘DOCUMENT_ROOT’]
$_SERVER[‘DOCUMENT_ROOT’] makes possible the use of relative paths in your
program
What happens if you don’t specify a path? Doing this sometimes is the easiest way to
programmatically manipulate files
We will not open files through FTP or HTTP
Problems with open files
We will not have problems with file permissions because the host and the client are on
the same computer and because we are running our programs as administrators.
The error suppression symbol on page 64 suppresses displays of error messages. We test
the file resource to find out if the operation succeeded or failed
Writing to a File
fwrite
See prototype on Page 66
File Formats
You can create your own file formats. You will use this freedom when you start using
MySQL. The example on page 66 uses tab characters to delimit data fields. The explode
function can recover the fields from the output string
Closing a file disconnects the program from the operating system; the program releases
the resources that it required when it opened the file
fclose
Knowing When to Stop feof
feof returns if a program has reached the end of a file. The file resource maintains a
variable called a file pointer. Every time the program reads data from a file the read
function add the number of bytes that it read to the file pointer. The program is at the end
of the file when the file pointer equals the number of bytes in the file.
Reading a Line at a Time:fgets, fgetss, and fgetcsv
Reading a line at a time is a good idea when you are reading very large files and you
don’t think you can read the whole file into memory
fgets is good for reading lines that you are not going to format
fgetcsv is good for reading lines that are made up of character delimited fields. fgetcsv
stores the fields for a line in an array.
Please explain the syntax diagram for fgetscv on page 71
Reading the Whole File:readfile, fpassthru, and file
We are not too interested in readfile
We are not too interested in fpassthru
We like the file function. The file function returns the contents of the file as an array.
Each line of the file is an element of the array
Reading a Character:fgetc
We could read the file character by character but then we would have to rebuild the data
from the strings of characters. We do not like the fgetc function
Reading an Arbitrary Length: fread
We are not too interested in fread either. People usually read and write text files one line
at a time or, if the text file is small, in one chunk
Using Other Useful File Functions
file_exists, filesize, unlink, rewind, fseek, ftell
file_exists or something like it is very useful; filesize is not very useful; unlink may prove
useful in the future; fseek and ftell are not very useful in variable line-length text files; in
fixed line-length text files they are very useful
Locking Files
Locking is meaningless on our computers because no one else will try to access the files
at the same time that we access them. File Locking manages concurrent access to
resources. We will look at locks again when we get into MySQL. We will not be able to
test file locking as long as we cannot put our files on a remote server.
Doing It a Better Way: Database Management Systems
Problems with Using Flat Files
Our flat files will not grow too large; we can do simple linear searches of arrays that we
build from flat files – this would be impossible for very large flat files; again we can do
random processing of arrays
How RDBMSs Solve These Problems
We will worry about this when we get to our own RDBMS MySQL.
Chapter 3 Using Arrays
Arrays interest primarily because we will use them to store the contents of database
records in memory
What is an Array?
An array is a collection of data that is stored contiguously in memory
Numerically Index Arrays
How do you create an array? See page 80 and page 81
Accessing Array Contents
How do you access an array’s contents?
You apply the array operator [] to the array name and the element index. An array
consists of data that we access by a number called an index. If you want the first element
of the array fred then you write fred[0].
Our book shows us how to create an initialized array. How do we create an initialized
array? How do we increase or decrease the size of an array?
Using Loops to Access the Array
Arrays with Different Indices
These are called associative arrays. The indices are strings called keys; the elements are
of arbitrary type and they are called values
Using Loops
foreach operator
The code on page 84 is very complex. The loop is doing a lot of work behind the scenes.
It updates $element until it looks at every element in the array. The each function is
called an iterator
list operator
Array Operators
See page 85
Multidimensional Arrays
PHP implements multidimensional arrays as arrays of arrays
The array on page 86 has numeric indices. The value of $products[0][0] is ‘TIR’; the
value of $products[0][2] is 100. Why?
You can mix numeric indexed arrays and string indexed arrays
Sorting Arrays
We do not care about sorting arrays
Using assort and ksort to Sort Arrays
Sorting in Reverse
Sorting Multidimensional Arrays
User-Defined Sorts
Reverse User Sorts
Reordering Arrays
We don’t care about reordering arrays
Using shuffle
We don’t care about using shuffle
Using array_reverse
We don’t care about using array reverse
Loading Arrays from Files
We do care about loading arrays from files
The example in the book uses the file function to create an array of orders from the
contents of a file and then echo the array to the standard output
Please explain the count function on page 97
Please explain the explode function on page 98
Performing Other Array Manipulations
Navigating Within an Array: each, current, reset, end, next, pos, and prev
These are interesting functions. They below to a class of functions called iterators. We
are not going to do too much with these functions
Applying Any Function to Each Element in an Array: array_walk
array_walk does not interest us very much
Counting Elements in an Array: count, sizeof, and array_count_values
Converting Arrays to Scalar Variables:extract
extract is an interesting function but we will not use it very much
Chapter 4 String Manipulation and Regular Expressions
Do you remember the string concatenation operator?
We don’t care very much about this chapter right now. We will come back to it later
Formatting Strings
Trimming Strings: chop, ltrim, rtrim, and trim
Formatting Strings for Presentation
Using HTML Formatting: The n12br function
Formatting a String for Printing
What is the difference between sprintf and printf?
Please explain the conversion specification. See page 110
We will have much need of sprintf
Changing the Case of a String
strtoupper, strtolower, ucfirst, ucwords
What is the difference between ucfirst and ucwords?
Formatting Strings for Storage:addslashes and stripslashes
These functions convert PHP strings to MySQL strings. MySQL cannot on its own
distinguish between some control characters and some literal characters. We use an
escape character \ to tell MySQL that the character that appears after the escape
character is a literal character. Use addslashes to format the string for the database. Use
stripslashes to remove the slashes
magic_quotes_gpc is off for our system. We should find out how to turn it on
Joining and Splitting Strings with String Functions
Using explode, implode, and join
Using strtok
strok is a string iterator
Using substr
string substr(string string, int start[, length’)
Comparing Strings
strcmp, strcasecm, and strnatcmp, strnatcasecmp
What is natural order of striings?
Matching and Replacing Substrings with String Functions
Finding Strings in Strings:strstr, strchr, strrchr, and stristr
Finding the Position of a Substring:strops and strrpos
Replacing Substrings:str_replace and substr_replace
Introducing Regular Expressions
Regular expression are very interesting but we will skip them for now.
Chapter 2
What is a text file?
What does it mean to open a file?
How do you open a file in PHP?
What is a File Mode?
What is the significance of the document root directory?
What is the significance of the parent directory of the document root directory?
Why do you want to avoid putting absolute paths in your PHP programs?
How do you read data from a file?
How do you write data to a file?
Why do you close files?
How does the feof function work?
How does PHP test for a file’s existence?
How does PHP test for a file’s size?
How does PHP delete a file?
How does PHP navigate inside files?
What is the file pointer?
How does rewind work?
How does fseek work?
How does ftell work?
What is a resource?
How do you lock files?
Why do you lock files?
What problems are associated with using flat files?
Chapter 3
What is an array?
What is an array index?
What is an associative array?
What is the range function?
What is the relation between loops and arrays?
How does PHP assign initial values to arrays?
What is the relation between arrays and files?
Can you explain the array operators?
What is multidimensional array?
How does PHP sort arrays?
How does PHP sort multidimensional arrays?
How does PHP allow a programmer to apply custom sorts to arrays?
How does the shuffle function work?
How does the array_reverse function work?
How does PHP load arrays from files?
How does PHP uses the each, current, reset, end, next, pos , and prev functions?
How does PHP use the array_walk function?
How does PHP count the elements of an array?
How does PHP convert arrays to scalars?
Chapter 4
What does the term “trim” mean as it applies to string?
How does PHP trim strings?
What does the n12br function work?
How does PHP format strings for printing?
How does PHP change the case of a string?
How does PHP use addslashes to format strings?
How does PHP use stripslashes to format strings?
How does PHP join strings?
How does PHP split strings?
How does PHP compare strings?
How does PHP determine a string’s length?
How does PHP match substrings?
How does PHP replace sub strings?
How does PHP search sub strings?
What is a regular expression?
How does PHP use regular expressions to match string patterns?