EECS1012. Net-centric Introduction to Computing. More PHP: Arrays and Files

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1 EECS 1012 EECS1012 Net-centric Introduction to Computing More PHP: Arrays and Files 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. M.S. Brown, EECS York University 1 (Creative Commons) Michael S. Brown, 2017.

2 2 Arrays

3 Arrays 3 <?php $food = array("falafel", "pide", "poutine"); print "I like to eat $food[0] and $food[2] ";?> PHP I like to eat falafel and poutine. output An array stores multiple values accessible by a single variable name We can access the value sin the array using an index or key. EECS CS1012

4 Indexed Arrays 4 <?php $food = array("falafel", "pide", "poutine"); print "My favorite is $food[0] \n";?> PHP 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. $food [index] array value "falafel" "pide" "poutine" EECS 1012

5 Indexed array syntax 5 $var[ index ] Array variable name index (sometimes called "offset") that you want to access within brackets [ ]

6 Array() function 6 <?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. $num [index] array value Indexed arrays are similar to how we accessed individual characters in string variables.

7 Manual array assignment 7 <?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.

8 print_r function 8 <?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.

9 Appending an array 9 <?php $a = array("css", "HTML", "PHP"); Array $a[] = "Java Script"; ( print_r($a); [0] => CSS?> PHP [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

10 Associative Arrays 10 <?php $age = array("peter"=>"35", "Ben"=>"37", "Joe"=>"43"); print $age["peter ]; print \n ; print $age[ Joe ];?> PHP output 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.

11 Associative array syntax 11 $var[ key ] Array variable name name of the key that you want to access within brackets [ ]

12 Associative arrays using array() 12 $a = array("peter"=>"35", "Ben"=>"37", "Joe"=>"43"); key is a string value is a string $a = array(1 => "Five", 2 => "Two", 3 => "Three"); key is a number value 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.

13 Associative array example 13 <?php $a["lecture"] = "Hall A"; $a["labs"] = "William Small 106"; $a["university"] = "York"; $a["college"] = "Lassonde"; print_r($a);?> You can also manually assign data to associative arrays. Array ( [lecture] => Hall PHPA [labs] => William Small 106 [university] => York [college] => Lassonde ) output EECS 1012

14 Printing array values 14 <?php $prez[0] = "Obama"; $prez[1] = "Trump"; $prez[2] = "Bush"; print "First $prez[2], then $prez[0], now $prez[1].. \n"; PHP First Bush, then Obama, now Trump... output We can print out indexed arrays just like other variables EECS 1012

15 Printing array with string keys 15 $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

16 Arrays are used like other variables 16 $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

17 Arrays are used like other variables 17 $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

18 Expression breakdown 18 $name = $a["first"]. " ". $a["last"]; "Abdel". " ". "Zhang"; "Abdel ". "Zhang"; "Abdel Zhang"; $name = "Abdel Zhang"; EECS 1012 (1) access values from the two associative arrays (2) apply the first concatenation operator with "Abdel" and " ". (3) apply seccond concatenation operator with "Abdel " and "Zhang" (4) assign result to variable $name

19 Accessing arrays using variables 19 $a = array("pide", "Dosa", "Falafel", "Poutine"); print "I like the following foods "; for($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

20 count function for arrays 20 $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

21 Simple array code example 21 <?php $names = array("abdel", "Xiong", "Tyler", "Mahsa", "Lili", "Deaner", "Tony", "Saeed"); EECS 1012 for($i=0; $i < count($names); $i++) { print "Student $i has name $names[$i] \n"; } Student 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 Output PHP

22 Some useful array functions 22 Function array_rand(a) count(a) array_sum(a) in_array(val, a) shuffle(a) sort(a) array_keys(a) Description Returns a randomly chosen index that is valid for array a returns the number of elements in an array Sums up all the values in the array Returns "true" if the given value is found in the array a rearranges the order of an array sorts the contents of array a returns an indexed array of all the keys in an associative array a EECS 1012

23 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

24 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"; } EECS 1012 Student 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 PHP Output

25 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

26 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

27 27 More on strings

28 28 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 address studentid Name address studentid Name address studentid

29 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

30 Functions explode and implode 30 Name explode(delim, s) implode(delim, a) What does it do? Takes a string, s, and breaks it up into multiple strings based on the delimiter, delim. The result is an array of string. Takes an array of strings, a, and places them back into a single string separated by the delimiter, delim. EECS 1012

31 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!

32 Explode - example 32 # imagine we read this string this from a file $bigstring = "Abdel abdel@gmail.com \n". "Lili lili@yahoo.com \n". "George xi@yorku.ca \n". "Xiong batman@136.com "; 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 EECS 1012 Number of students = 4 output

33 Explode breakdown 33 $bigstring = "Abdel abdel@gmail.com \n". "Lili lili@yahoo.com \n". "George xi@yorku.ca \n". "Xiong batman@136.com "; $eachline = explode("\n", $bigstring); The delimiter that specifies the boundaries of what want to separate. The string that we want to explode. EECS 1012

34 What is the result? 34 Explode returns an array that contains the strings that have been separated by the delimiter. $eachline = explode("\n", $bigstring); print_r($eachline) Array ( [0] => Abdel abdel@gmail.com [1] => Lili lili@yahoo.com [2] => George xi@yorku.ca [3] => Xiong batman@136.com )

35 Going further 35 # imagine we read this string this from a file $bigstring = "Abdel abdel@gmail.com \n". "Lili lili@yahoo.com \n". "George xi@yorku.ca \n". "Xiong batman@136.com "; $eachline = explode("\n", $bigstring); # this is an array for ($i = 0; $i < count($eachline); $i++) { $info = explode( " ", $eachline[$i]); print_r($info); } PHP

36 36 Going further $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 $info[2] is the studentid Array ( [0] => Abdel abdel@gmail.com [1] => Lili lili@yahoo.com [2] => George xi@yorku.ca [3] => Xiong batman@136.com ) Array ( [0] => Abdel [1] => abdel@gmail.com [2] => ) Array ( [0] => Lili [1] => lili@yahoo.com [2] => ) Array ( [0] => George [1] => xi@yorku.ca [2] => ) Array ( [0] => Xiong [1] => batman@136.com [2] => )

37 Yet even further $bigstring = "Abdel abdel@gmail.com \n". "Lili lili@yahoo.com \n". "George xi@yorku.ca \n". "Xiong batman@136.com "; $eachline = explode("\n", $bigstring); # break into lines print "<table> \n"; print "<tr> <th> Name </th> <th> </th> <th> Student ID </th> </tr> \n"; for ($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";

38 A Table with a few lines of code! 38 Output from previous slide's PHP code.. <table> <tr> <th> Name </th> <th> </th> <th> Student ID </th> </tr> <tr> <td> Abdel </td> <td> abdel@gmail.com </td> <td> </td> </tr> <tr> <td> Lili </td> <td> lili@yahoo.com </td> <td> </td> </tr> <tr> <td> George </td> <td> xi@yorku.ca </td> <td> </td> </tr> <tr> <td> Xiong </td> <td> batman@136.com </td> <td> </td> </tr> </table> With just a few lines of code, we have created a table from our original big string! See example here

39 Implode function 39 Takes an array and forms a big string inserting the specified delimiter $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

40 Implode explained 40 $names = Array ( [0] => Abdel [1] => Xiong [2] => Tyler [3] => Mahsa [4] => Lili [5] => Deaner [6] => Tony [7] => Saeed ) $allnames = implode(",", $names); EECS 1012 Make a single string by concatenating all the content with this delimiter inserted between each item. array to implode

41 Impode example 41 $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.

42 Array/string recap 42 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 EECS 1012

43 43 PHP File Input/Output

44 Files 44 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. EECS 1012

45 PHP file diagram 45 Text File Text file that is on the server. EECS 1012 PHP can access this file and incorporate its contents into the output. PHP can also write information to this file.

46 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.

47 Basic PHP file I/O functions 47 function name file(filename) file_get_contents(filename) file_put_contents(filename, data, mode) file_exists(filename) category Reads the contents from a file with the name filename into an array of strings, where each string is a line from the file. Reads the contents from a file with the name filename into one large string. Write content from data to a file with the name filename, using a particular writing mode. Checks to see if a file of filename exists. There are many types of file functions for PHP, we will learn these two basic functions. I/O is computing speak for "Input/Output"

48 Reading from a file 48 File: foo.txt Hello how are you? I'm fine file("foo.txt") array( "Hello\n", #0 "how are\n", #1 "you?\n", #2 "\n", #3 "I'm fine\n" #4 ) file_get_contents ("foo.txt") "Hello\n how are\n you?\n \n I'm fine\n" file returns lines of a file as an array file_get_contents returns entire contents of a file as a string EECS CS1012

49 Example quotes.txt 49 Assume I have a file named "quotes.txt" in my webserver directory (e.g. www folder). This file has a quote on each line. quotes.txt "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 EECS 1012

50 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

51 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 strint print $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

52 Writing to a file 52 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); EECS 1012 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 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

53 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); EECS 1012 When the FILE_APPEND parameter is passed to file_put_contents, new content will be appended to the end of the file. 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. File: square_table.txt. 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.

54 Recap 54 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 EECS 1012