intro to php - department of electrical engineering...
TRANSCRIPT
EECS1012Net-centric Introduction
to Computing
M.S. Brown, EECS – York University 1
More PHP: Arrays and Files
EECS 1012
Acknowledgements
Contents are adapted from web lectures for “Web Programming Step by Step”, by M. Stepp, J. Miller, and V. Kirst.
Slides have been ported to PPT by Dr. Xenia Mountrouidou.
These slides have been edited for EECS1012, York University.
The contents of these slides may be modified and redistributed, please give appropriate credit.
(Creative Commons) Michael S. Brown, 2017.
Arrays2
Arrays3
<?php$food = array("falafel", "pide", "poutine");print "I like to eat $food[0] and $food[2] ";
?> PHP
An array stores multiple values accessible by a
single variable name
We can access the value sin the array using an
“index” or “key”.
CSEECS 1012
I like to eat falafel and poutine. output
Indexed Arrays4
Index arrays (or numerical arrays) are arrays
where the individual values in the array are access
with a numeric index. Indexing starts at position 0,
not 1.
<?php$food = array("falafel", "pide", "poutine");print "My favorite is $food[0] \n";
?> PHP
0 1 2
"falafel" "pide" "poutine"
[index]
array value
$food
EECS 1012
Indexed array syntax5
$var[ index ]
Array variable name index (sometimes called "offset")
that you want to access
within brackets [ ]
Array() function6
<?php$num = array(100, 90, 80, 70, 60, 50, 40, 30, 20, 10);print $num[0]; # output would be 100
?> PHP
The function array() can be used to create an
array variable as shown above. In this example,
the data in the array are integers.
0 1 2 3 4 5 6 7 8 9
100 90 80 70 60 50 40 30 20 10
[index]
array value
$num
Indexed arrays are similar to how we accessed individual characters in string variables.
Manual array assignment7
<?php$food[0] = "dosa";$food[1] = "pide";$food[2] = "poutine";
print "I like to eat $food[0] and $food[2] ";?> PHP
I like to eat dosa and poutine. output
We can manually assign values to an array.
This example did not use the array function, but the
result is identical.
print_r function8
<?php$array_var = array( "CSS", "PHP", "HTML", "Coding" );
print_r($array_var);
?> PHP
Array
(
[0] => CSS
[1] => PHP
[2] => HTML
[3] => Coding
) output
This function is referred to as the "Print Readable" function and helps you visualize
the contents of your data. You can use it with arrays or other data types.
Appending an array 9
<?php
$a = array("CSS", "HTML", "PHP");$a[] = "Java Script";print_r($a);
?> PHP
Array
(
[0] => CSS
[1] => HTML
[2] => PHP
[3] => Java Script
) output
If you assign a value to an array without an index
specified, e.g. $a[ ] = "Hello", PHP will append the
new value at the "end" of the current array.
EECS 1012
Associative Arrays10
<?php$age = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");print $age["Peter“];print “\n”;print $age[“Joe”];
?> PHP
35
43output
Associative arrays uses a “key” to access an
individual element in the array.
Syntax: $var_name[ key ]. The key is often a
string, but can also be a numerical value.
Associative array syntax11
$var[ key ]
Array variable name name of the key that you want
to access within brackets [ ]
Associative arrays using array()12
$a = array("Peter"=>"35", "Ben"=>"37", "Joe"=>"43");
key is
a stringvalue is a string
$a = array(1 => "Five", 2 => "Two", 3 => "Three");
key is
a numbervalue is a string
Syntax to specify in the array() function: key => value. You will
generally string values used as keys, but numerical values can also be
used as shown above.
Associative array example13
<?php
$a["lecture"] = "Hall A";$a["labs"] = "William Small 106";$a["university"] = "York";$a["college"] = "Lassonde";
print_r($a); ?> PHP
Array
(
[lecture] => Hall A
[labs] => William Small 106
[university] => York
[college] => Lassonde
)output
You can also manually assign
data to associative arrays.
EECS 1012
Printing array values14
<?php$prez[0] = "Obama";$prez[1] = "Trump";$prez[2] = "Bush";
print "First $prez[2], then $prez[0], now $prez[1] . . \n";PHP
We can print out indexed arrays just like other
variables
First Bush, then Obama, now Trump . . .
output
EECS 1012
Printing array with string keys15
$a["university"] = "York";$a["college"] = "Lassonde";
print "EECS is in the {$a["college"]} college \n";PHP
When we print array values with string keys, we
need to place them within { } in the print statement
EECS 1012
Arrays are used like other variables16
$a = array( 5, 10, 15, 20, 25, 30 ); $a[0] = $a[0] + 10; // $a[0] now equals 15 $a[1]++; // $a[1] now equals 11 $a[2] = $a[3] + $a[5]; // $a[2] now equals 50 print_r($a);
PHP
The math operations in
this example are just like
we saw for non-array
variables in the last lecture notes.
Array
(
[0] => 15
[1] => 11
[2] => 50
[3] => 20
[4] => 25
[5] => 30
) OUTPUT
Arrays are used like other variables17
$a = array( "first" => "Abdel", "last" => "Zhang" );
$anme = $a["first"] . " " . $a["last"];
print "$name \n";
PHP
Abdel Zhang
OUTPUT
In this example the associative array values are accessed using keys. They are
concatenated together (with a space in the middle) to form a larger string.
EECS 1012
Expression breakdown18
EECS 1012
$name = $a["first"] . " " . $a["last"];
"Abdel" . " " . "Zhang";
"Abdel " . "Zhang";
"Abdel Zhang";
(1) access values
from the two
associative arrays
(2) apply the first
concatenation oper-
ator with "Abdel"
and " ".
(3) apply seccond
concatenation oper-
ator with "Abdel "
and "Zhang"
(4) assign result to
variable $name
$name = "Abdel Zhang";
Accessing arrays using variables19
$a = array("Pide", "Dosa", "Falafel", "Poutine");
print "I like the following foods ";for($i=0; $i < 4; $i++){
print "($i) $a[$i] ";} PHP
I like the following foods: (1) Pide (2) Dosa (3) Falafel (4) Poutine output
We can use a variable's value to access the index.
In the above example, $i, is used to access the
values in array $a
count function for arrays20
$a = array("Pide", "Dosa", "Falafel", "Poutine");$a_length = count($a);print "The number of items in the array is $a_length. \n";
PHP
The number of items in the array is 4. output
count(a) returns the number of elements in the array
a. Sometimes we call this the "size" of the array, or
"length" of the array.
EECS 1012
Simple array code example21
<?php
$names = array("Abdel", "Xiong", "Tyler", "Mahsa", "Lili", "Deaner", "Tony", "Saeed");
for($i=0; $i < count($names); $i++){
print "Student $i has name $names[$i] \n";}
PHPStudent 0 has name Abdel
Student 1 has name Xiong
Student 2 has name Tyler
Student 3 has name Mahsa
Student 4 has name Lili
Student 5 has name Deaner
Student 6 has name Tony
Student 7 has name Saeed OutputEECS 1012
Some useful array functions22
Function Description
array_rand(a) Returns a randomly chosen index that is
valid for array a
count(a) returns the number of elements in an array
array_sum(a) Sums up all the values in the array
in_array(val, a) Returns "true" if the given value is found in
the array a
shuffle(a) rearranges the order of an array
sort(a) sorts the contents of array a
array_keys(a) returns an indexed array of all the keys in
an associative array a
EECS 1012
Examples – array_rand()23
<?php
$names = array("Abdel", "Xiong", "Tyler", "Mahsa", "Lili", "Deaner", "Tony", "Saeed");
$lucky = array_rand($names); # selects a random index!
print "$names[$lucky] gets an A for EECS1012 \n";
PHP
Deaner gets an A for EECS1012
EECS 1012
Examples – sort()24
<?php
$names = array("Abdel", "Xiong", "Tyler", "Mahsa", "Lili", "Deaner", "Tony", "Saeed");
sort($names); # this sorts the array, place result back in# the same variable
for($i=0; $i < count($names); $i++){
print "Student $i has name $names[$i] \n";}
PHPStudent 0 has name Abdel
Student 1 has name Deaner
Student 2 has name Lili
Student 3 has name Mahsa
Student 4 has name Saeed
Student 5 has name Tony
Student 6 has name Tyler
Student 7 has name Xiong OutputEECS 1012
Examples – array_keys()25
$items= array("iPhone" => 988, "Samsung" => 700, "LG" => 500);
$keys = array_keys( $items ); # returns an array with the keys from# items
for($i=0; $i < count($keys); $i++) {
$key = $keys[$i]; print "Item: $i Brand: $key Price: $ $items[$key] \n";
}
PHP
Item: 0 Brand: iPhone Price: $ 988
Item: 1 Brand: Samsung Price: $ 700
Item: 2 Brand: LG Price: $ 500
OUTPUT
Examples – in_array()26
$class = array("Abdel", "Mahmoud", "Sam", "Tyler", "Susan", "Kyros");
$find_person = "Pasha";
if (in_array($find_person, $class)) # function returns TRUE or FALSE{
print "$find_person is enrolled. \n";}else{
print "$find_person is not enrolled. \n";}
PHP
Pasha is not enrolled.
OUTPUT
More on strings27
Processing strings
The vast majority of content we will manipulate in
web programming is text. Text is best represented
using string types.
Text is often organized (or semi-organized) into
some type of structure, e.g.
Class list
Name | email address | studentID
Name | email address | studentID
Name | email address | studentID
28
More on strings (and arrays)29
Now that we know how to use arrays, we can
revisit string functions
There are many functions to process strings that
return arrays of strings are their result, or that
take arrays as their parameters
We will examine two very useful string
functions: implode and explode
Functions explode and implode30
Name What does it do?
explode(delim, s)
Takes a string, s, and breaks it
up into multiple strings based
on the delimiter, delim. The
result is an array of string.
implode(delim, a)
Takes an array of strings, a,
and places them back into a
single string separated by the
delimiter, delim.
EECS 1012
What is a delimiter?31
A sequence of one or more symbols
used to specify the boundary
between independent regions.
You use delimiters all the time!
If you didn't add a space delimiter,
text would be unreadable!
https://en.wikipedia.org/wiki/Delimiter
Explode - example32
# imagine we read this string this from a file $bigString = "Abdel | [email protected] | 1238203 \n" .
"Lili | [email protected] | 123888 \n" ."George| [email protected] | 304304 \n" . "Xiong | [email protected] | 111000 ";
print $bigString;
$eachLine = explode("\n", $bigString); # this is an array$numberOfLines = count($eachLine); # this is the size
# the array "eachLine"
print "Number of students = $numberOfLines \n";
PHP
Number of students = 4 outputEECS 1012
Explode – breakdown33
$eachLine = explode("\n", $bigString);
$bigString = "Abdel | [email protected] | 1238203 \n" ."Lili | [email protected] | 123888 \n" ."George| [email protected] | 304304 \n" . "Xiong | [email protected] | 111000";
The string
that we want
to explode.
The delimiter that specifies the
boundaries of what want to separate.
EECS 1012
What is the result?
Explode returns an array that contains the strings
that have been separated by the delimiter.
34
Array
(
[0] => Abdel | [email protected] | 1238203
[1] => Lili | [email protected] | 123888
[2] => George| [email protected] | 304304
[3] => Xiong | [email protected] | 111000
)
$eachLine = explode("\n", $bigString);print_r($eachLine)
Going further35
# imagine we read this string this from a file $bigString = "Abdel | [email protected] | 1238203 \n" .
"Lili | [email protected] | 123888 \n" ."George| [email protected] | 304304 \n" . "Xiong | [email protected] | 111000 ";
$eachLine = explode("\n", $bigString); # this is an array
for ($i = 0; $i < count($eachLine); $i++) {
$info = explode( "|", $eachLine[$i]);print_r($info);
}PHP
Going further36
Array
(
[0] => Abdel | [email protected] | 1238203
[1] => Lili | [email protected] | 123888
[2] => George| [email protected] | 304304
[3] => Xiong | [email protected] | 111000
)
Array
(
[0] => Abdel
[1] => [email protected]
[2] => 1238203
)
Array
(
[0] => Lili
[1] => [email protected]
[2] => 123888
)
Array
(
[0] => George
[1] => [email protected]
[2] => 304304
)
Array
(
[0] => Xiong
[1] => [email protected]
[2] => 111000
)
$eachLine = explode("\n", $bigString);
for ($i = 0; $i < count($eachLine); $i++) {$info = explode( "|", $eachLine[$i]);print_r($info);
}
With two applications of "explode" functions, we have
taken our original string and broke it first into lines,
then each line into the basic "info".
$info[0] is the name
$info[1] is the email
$info[2] is the studentID
Yet even further. . . 37
$bigString = "Abdel | [email protected] | 1238203 \n" ."Lili | [email protected] | 123888 \n" ."George| [email protected] | 304304 \n" . "Xiong | [email protected] | 111000 ";
$eachLine = explode("\n", $bigString); # break into lines
print "<table> \n";print "<tr> <th> Name </th> <th> Email </th> <th> Student ID </th> </tr> \n";
for ($i = 0; $i < count($eachLine); $i++) {$info = explode( "|", $eachLine[$i]); # break line into data# print this out to table!print "<tr><td> $info[0] </td> <td> $info[1] </td> <td> $info[2] </td></tr>\n";}
print "</table> \n";
A Table with a few lines of code!38
<table>
<tr> <th> Name </th> <th> Email </th> <th> Student ID </th> </tr>
<tr> <td> Abdel </td> <td> [email protected] </td> <td> 1238203 </td> </tr>
<tr> <td> Lili </td> <td> [email protected] </td> <td> 123888 </td> </tr>
<tr> <td> George </td> <td> [email protected] </td> <td> 304304 </td> </tr>
<tr> <td> Xiong </td> <td> [email protected] </td> <td> 111000 </td> </tr>
</table>
With just a few lines of code, we have created a table from our
original big string!
See example here
Output from previous slide's PHP code. .
Implode function
Takes an array and forms a big string inserting the
specified delimiter
39
$names = array("Abdel", "Xiong", "Tyler", "Mahsa", "Lili","Deaner", "Tony", "Saeed");
$allNames = implode(",", $names);
print '$names is of type ' . gettype($names) . "\n"; print '$allNames is of type ' . gettype($allNames) . "\n";print '$names = '; print_r($names); print '$allNames = '; print_r($allNames);
See code here
Implode – explained40
$allNames = implode(",", $names);
array to implodeMake a single string by concatenating
all the content with this delimiter inserted
between each item.
$names = Array
(
[0] => Abdel
[1] => Xiong
[2] => Tyler
[3] => Mahsa
[4] => Lili
[5] => Deaner
[6] => Tony
[7] => Saeed
)
EECS 1012
Impode example41
$allNames = implode(",", $names); print $allNames;
PHP
Abdel,Xiong,Tyler,Mahsa,Lili,Deaner,Tony,Saeed
Output
This example took our array of names and created a single string with a delimiter
inserted between each item in the array.
Array/string recap
Arrays are useful data types to store a collection of
data using the same variable name
Two types of arrays: indexed and associative
Many string functions return their results as arrays,
or accept arrays as input
42
EECS 1012
PHP File Input/Output43
Files
File are stored on our "hard drives" – the data
remains there even when the computer is turned off.
We can read and write data to files. These files
are generally stored on the web server.
PHP can read this data into the program.
PHP can also write out information to files.
44
EECS 1012
PHP file diagram45
Text
File
Text file that
is on the server.
PHP can access
this file and
incorporate
its contents into the
output. PHP can
also write information
to this file.
EECS 1012
Facebook has a file on all of you!46
Deaner's File
Likes: Poutine, Beer, Smokes, Hockey
Posts: Just Give'r Terry, …, …, …
Friends: Tron, Terry, Ron
Facebook stores all your information, posts, likes, etc in
files that it accesses each time you log in. It also shares
this information with vendors who want to sell you things.
Basic PHP file I/O functions
function name category
file(filename)
Reads the contents from a file with the
name filename into an array of
strings, where each string is a line
from the file.
file_get_contents(filename)Reads the contents from a file with the
name filename into one large string.
file_put_contents(filename, data, mode)
Write content from data to a file with
the name filename, using a particular
writing mode.
file_exists(filename)Checks to see if a file of filename
exists.
47
I/O is computing speak for "Input/Output"There are many types of file functions for PHP, we will learn these two basic functions.
Reading from a file
file("foo.txt")file_get_contents
("foo.txt")
array(
"Hello\n", #0
"how are\n", #1
"you?\n", #2
"\n", #3
"I'm fine\n" #4 )
"Hello\n
how are\n
you?\n
\n
I'm fine\n"
CS
48
file returns lines of a file as an array
file_get_contents returns entire contents of a file as a
string
EECS 1012
Hello
how are
you?
I'm fine
File: foo.txtFile: foo.txt
Example – quotes.txt
Assume I have a file named "quotes.txt" in my
webserver directory (e.g. www folder).
This file has a quote on each line.
49
"If you want to achieve greatness stop asking for permission." --Anonymous
"Things work out best for those who make the best of how things work out." --John Wooden
"To live a creative life, we must lose our fear of being wrong." –Anonymous
…
…
…
quotes.txt
EECS 1012
Reading a file using file()50
# opens the file and reads content in – each line is placed into an # array $quotes = file("quotes.txt");
# randomly select an index in this array$i = array_rand($quotes);
# convert the $quotes[$i] to special characters # (e.g. " becomes ")$output = htmlspecialchars($quotes[$i]);
print "<p> <quote> $output </quote> </p> \n";
<p> <quote> "Successful entrepreneurs are givers and not takers of positive
energy." --Anonymous
</quote> </p> OUTPUT
EECS 1012
Reading using file_get_content()51
# opens the file and reads content in as one big string$content = file_get_content("quotes.txt");
# convert the string to all upper case$content = strtoupper ( $content );
# print the strintprint $content;
"IF YOU WANT TO ACHIEVE GREATNESS STOP ASKING FOR PERMISSION." --ANONYMOUS
"THINGS WORK OUT BEST FOR THOSE WHO MAKE THE BEST OF HOW THINGS WORK
OUT." --JOHN WOODEN
"TO LIVE A CREATIVE LIFE, WE MUST LOSE OUR FEAR OF BEING WRONG." --ANONYMOUS
"IF YOU ARE NOT WILLING TO RISK THE USUAL YOU WILL HAVE TO SETTLE FOR THE
ORDINARY." --JIM ROHN
…. OUTPUT
Writing to a file52
for($i=0; $i < 10; $i++){$square = $i * $i;$output[] = "$i * $i = $square \n"; # appends to array
}
# writes an array of strings to the file.file_put_contents("square_table.txt", $output);
0 * 0 = 0
1 * 1 = 1
2 * 2 = 4
3 * 3 = 9
4 * 4 = 16
5 * 5 = 25
6 * 6 = 36
7 * 7 = 49
8 * 8 = 64
9 * 9 = 81
If the file doesn't already
exisit, this creates a file
named "square_table.txt"
and places the following
content in it. If the file did
already exist, this overrides
the content in the file. So,
be careful with file writing!
File: square_table.txt
EECS 1012
Appending to a file (FILE_APPEND)53
for($i=0; $i < 10; $i++){$square = $i * $i;$output[] = "$i * $i = $square \n"; # appends to array
}
file_put_contents("square_table.txt", $output, FILE_APPEND);
If the file already exists, this writes
the data to the end of the file. If the
file doesn't exist, it creates a new file.
….
0 * 0 = 0 (Added to
1 * 1 = 1 the end of
2 * 2 = 4 the existing
3 * 3 = 9 file)
4 * 4 = 16
5 * 5 = 25
6 * 6 = 36
.
File: square_table.txtWhen the FILE_APPEND parameter
is passed to file_put_contents, new
content will be appended to the
end of the file.
EECS 1012
Recap
Basic File I/O is very easy in PHP
File content can be easily read in as an array or a
string
Data can be easily written out to files.
NEXT UP: getting information from HTML files
through forms
54
EECS 1012