PHP – Working with Files and Strings

1. PHP – Working with Files and Strings Stewart Blakeway FML 213 blakews@hope.ac.uk

2. What will we cover • How to format strings • Determining a string length • How to find a string within a string • Breaking down a string into component parts • Removing white spaces from a string

3. Why? • As part of your assessment marking criteria you are marked on how you present information • If you can format your text you will score higher on that aspect of the mark sheet

4. Strings • What is a string? • Two characters or more, a word, a sentence, a paragraph and so-forth • Until now we have only passed strings to functions or echoed them out. Sometimes you will want to manipulate the text within a string

5. printf() function • printf() is based on the function originally written in C • It works like the echo function with the advantage of automatically converting an integer or float • It also has the advantage of accepting parameters from the end of the statement to be included anywhere in the string

6. printf() <?php $num1=20.5; printf ("The original number is: %f<br>",$num1); printf ("Now it is: %d <br>",$num1); printf ("Now it is: %b <br>",$num1); echo ($num1); ?>

7. printf() %d Decimal (base 10) %b Binary (base 2) %c Integer as ASCII equivalent %f Float %o Octal (base 8) %s String %x Hexadecimal (base 16)

8. Padding and Printf() • by default all leading zeros and spaces will be omitted from a string • You can force leading zeros or spaces to be displayed by using the padding specifier • %0

9. Leading Zeros • printf(“%010d”,36); • will print “0000000036”

10. Other characters • Other characters can be used instead of zeros • they must be followed by a single quotation mark printf(“%’*20d”,36); ******************36

11. Leading Spaces • You have to use the <pre> tag! • Multiple white spaces are ignored by the web browser. • You can force white space to be displayed by using the pre tag.

12. Using <pre> <pre> <?php printf(" Hello World!"); ?> </pre> • Will print the leading spaces. pre is the html tag that tells the browser to print as it appears!

13. Question What will be printed to screen? <?php <pre> printf(" Hello World!"); </pre> ?> Parse error: parse error, unexpected '<' in C:\Program Files\Apache Group\Apache2\htdocs\pre.PHP on line 9

14. How about now? <?php echo "<pre>"; printf(" Hello World!"); echo "</pre>"; ?>

15. Specifying a string length • You can specify a length of a string using the same technique seen in padding. <?php echo "<pre>"; printf("%20s<br />","Apples"); printf("%20s<br />","Bananas"); printf("%20s<br />","Pears"); echo "</pre>"; ?>

16. Specifying the string length • By default spaces are printed first • You can change this behaviour by using a - <?php echo "<pre>"; printf("%-20s\n","Apples"); printf("%-20s\n","Bananas"); printf("%-20s\n","Pears"); echo "</pre>"; ?>

17. String Length $file = fopen("student_list.txt","r"); while (!feof($file)) { echo "<pre>"; printf ("%100s<br />",fgets($file)); echo "</pre>"; }

18. Arrays and Strings • A string is an array of characters $test=“Hello World!” echo ($test[6]); W

19. Finding the length of a string • strlen() is a function that will return the length of a string $slength = strlen(“Hello World!”); echo ($slength); • This could be used for validation

20. What is echoed out? $studentID=("05001221222"); if (strlen ($studentID) > 10) { echo ("Student Number is too many characters!"); } else { echo ("Student Number accepted"); }

21. Examining the contents of a string • strstr() is a function that searches the string depending on a criteria you specify! $studentID=("05001221222"); if (strstr ($studentID,"0500")) { echo ("Student registered in 2005"); } else { echo ("Student did not register in 2005"); }

22. Another example $userString=("I heard Simon knows how to make bombs!"); if (strstr ($userString,"bomb")) { echo ("Warning! Text contains something about bombs!"); } else { echo ("Text contains no keywords posing a threat to the nation"); }

23. Final example stristr() – Not case sensitive $userString=("I heard Simon knows how to make Bombs!"); if (strstr ($userString,"bomb")) { echo ("Warning! Text contains something about bombs!"); } else { echo ("Text contains no keywords posing a threat to the nation"); }

24. Reporting the position of the found criteria • strpos() will report the position of the criteria found $userString=("I heard Simon knows how to make bombs!"); if (strstr ($userString,"bomb")) { echo ("Warning! Text contains something about bombs! <br>"); echo ("At position" . strpos($userString,"bomb")); } else { echo ("Text contains no keywords posing a threat to the nation"); }

25. Lets put it all together to create something useful! $naughtyWord = array ("bomb","detonate","detonator","tnt","explosion"); $userString=("I heard Simon knows how to make bombs! He uses tnt and a detonator to create a huge explosion!"); foreach ($naughtyWord as $currentWord) { if (strstr ($userString,$currentWord)) { echo ("Warning! Text contains naughty word: ".$currentWord); echo (" at position" . strpos($userString,$currentWord) . "<br>"); } }

26. Extracting specific text from a string • substr() will allow you to copy certain characters or a group of characters from a string! • They must be adjacent • You can start from the beginning or the end of the string

27. substr() $userString=("I heard Simon knows how to make bombs! He uses tnt and a detonator to create a huge explosion!"); echo (substr($userString, 8));

28. substr() $userString=("I heard Simon knows how to make bombs! He uses tnt and a detonator to create a huge explosion!"); echo (substr($userString, 8,5));

29. From the end of the string $userString=("I heard Simon knows how to make bombs! He uses tnt and a detonator to create a huge explosion!"); echo (substr($userString, -10,10));

30. How could this be useful? $userEmail=("blakews@hope.ac.uk"); if (substr($userEmail, -2,2) == "uk") { echo ("UK customers pay £5 postage"); } else { echo ("You are not based in the UK, postage is £15"); }

31. A further refinement $userEmail=("blakews@hope.ac.uk"); if (substr($userEmail, -2,2) == "uk") { echo ("UK customers pay £5 postage<br>"); if (substr($userEmail, -6) == ".ac.uk") { echo ("You work in education, you save a further 10%"); } } else { echo ("You are not based in the UK, postage is £15"); }

32. Splitting a string into new strings • Excel or Access for example will save a file as a text file using delimiters to separate each column • Sometimes you will want to split a string into a new string depending on delimiters • This is achieved by using the strtok() function

33. What is echoed out? $userString=("Hello everybody, it is a lovely day"); $delim = (" "); $word = (strtok($userString, $delim)); echo $word;

34. What about now? $userString=("Hello everybody, it is a lovely day"); $delim = (" "); $word = (strtok($userString,$delim)); $count=0; while (is_string($word)) { echo ($word."<br />"); $count++; $word = (strtok($delim)); } echo ($count. “words in the string”);

35. Sometimes you will want to remove white space from strings • trim () Deletes all white spaces from the right and left of the string • ltrim () Deletes all white spaces from the left of the string • rtrim () Deletes all white spaces from the right of the string $string = trim ($string);

36. strip_tags() • Strip tags is very useful for stripping html tags from a string $mytext = (“<h1>Hello World!</h1>”); echo strip_tags ($mytext);

37. Replacing a portion of the string • The substr_replace() function works like the substr() except it allows you to replace the section of the string $mystring = “Last updated 2001”; $mystring = substr_replace ($mystring, “2007”, -4, 4);

38. Converting Case • PHP provides 4 functions that manipulate the case of a string • strtoupper(); • strtolower(); • ucwords(); • ucfirst();

39. Example $mytext “heLLowORLd!” strtoupper($mytext); // HELLO WORLD! strtolower($mytext); // hello world! ucwords($mytext); // Hello World! ucfirst($mytext); // Hello world!

40. Breaking strings into arrays • PHP offers a function that will take a string of text and put each word into an array with a separate index $myarray= explode(“ ”, “Hello World!”); • Produces an array called $myarraywith two indexes. • $myarray[0] = “Hello”; • $myarray[1] = “World”;

41. Working Example • The objective is to allow the user to check their spelling • Get the users text • Compare each word with a valid word • If the word does not match a valid word, highlight the word dict.lst ======== a -> z

42. 1. Get users text function getUsersText() { echo (" <form id='form1' name='form1' method='post' action='$_SERVER[PHP_SELF]'> <p>Enter some text<br /> <textarea name='usersText' id='usersText' cols='45' rows='5'></textarea> </p> <p> <input type='submit' name='checkSpelling' id='checkSpelling' value='Check Spelling' /> </p></form> "); } • How do we get user input from the users? • Create a function called getUsersText • Create a form • action=‘$_SERVER[PHP_SELF]’ • Create a textarea called usersText

43. 2. Read in a dictionary • Create a function called buildDictionary • open a file for reading called dict.lst • while not end of the file read each line and put into an array called $word[] • return the array function buildDictionary () { $dictionary = fopen("dict.lst","r"); while (!feof($dictionary)) { $word[] = fgets($dictionary); } return $word; }

44. 3. Check Spelling • Create a function called checkSpelling • the function will receive two arguments • $userTextand $word • use the explode function to split the $userText into an array called $userWord • for each word in the array $userWordcheck against each word in the array $word • if a match is found, copy the word to a variable called $correctUsersTextwithout any formatting, else copy with bold formatting • return $correctUsersText

45. 3. Check spelling function checkSpelling($usersText, $word) { $usersWord = explode(" ",$usersText); foreach ($usersWord as $currentUserWord) { foreach ($word as $currentDictionaryWord) { if (trim($currentDictionaryWord) == trim($currentUserWord)) { $correctUsersText .= $currentUserWord . " "; $found = True; break; } } if (!$found) { $correctUsersText .= "<b>" . $currentUserWord . "</b> "; } $found = False; } return $correctUsersText; }

46. 4. Output the spelling mistakes • Create a function called display • accept one argument • echo the argument function display ($txt) { echo $txt; }

47. Putting it all together if (!isset($_POST['usersText'])) { getUsersText(); } else { $words = buildDictionary(); $correctUsersText = checkSpelling($_POST['usersText'],$words); display ($correctUsersText); } You should now be creating functions that mean something to you and perform a specific task. Sometimes you will want to pass values to the function so that is has something to work with Sometimes you will want an answer from a function

48. Spot the mistakes $mystring = “Last updated 2001” $mystring = substr_replace (mystring, “2007” -4, 4);

49. Spot the mistakes $userEmail=(blakews@hope.ac.uk); if (substr($userEmail, -2,2) == "uk" echo ("UK customers pay £5 postage"); else echo ("You are not based in the UK, postage is £15");

50. Summary Slide • Strings • printf() function • Padding and Printf() • <pre> </pre> tag • Specifying a string length • Arrays and Strings • Finding the length of a string • Reporting the position of the found criteria