PHP – Working with Files and Strings

www.hope.ac.uk Faculty of Sciences and Social Sciences

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PHP – Working with Files and Strings

Stewart Blakeway

FML 213

[email protected]


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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


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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


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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


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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


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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);?>


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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)


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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


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Leading Zeros

• printf(“%010d”,36);

• will print “0000000036”


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Other characters

• Other characters can be used instead of zeros

• they must be followed by a single quotation mark

printf(“%’*20d”,36);

******************36


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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.


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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!


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QuestionWhat will be printed to screen?

<?php

<pre>


</pre>

?>

Parse error: parse error, unexpected '<' in C:\Program Files\Apache Group\Apache2\htdocs\pre.PHP on line 9


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How about now?

<?php

echo "<pre>";


echo "</pre>";

?>


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Specifying a string length• You can specify a length of a string using the

same technique seen in padding.

<?phpecho "<pre>";printf("%20s<br />","Apples");printf("%20s<br />","Bananas");printf("%20s<br />","Pears");echo "</pre>";?>


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Specifying the string length• By default spaces are printed first• You can change this behaviour by using a -

<?phpecho "<pre>";printf("%-20s\n","Apples");printf("%-20s\n","Bananas");printf("%-20s\n","Pears");echo "</pre>";?>


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String Length$file = fopen("student_list.txt","r");

while (!feof($file))

{

echo "<pre>";

printf ("%100s<br />",fgets($file));

echo "</pre>";

}


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Arrays and Strings

• A string is an array of characters

$test=“Hello World!”

echo ($test[6]);

W


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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


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What is echoed out?$studentID=("05001221222");

if (strlen ($studentID) > 10){echo ("Student Number is too many characters!");

}

else{echo ("Student Number accepted");}


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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");

}


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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");

}


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Final 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");

}

stristr() – Not case sensitive

http://www.php.net/manual/en/function.stristr.php

http://www.php.net/manual/en/function.stristr.php


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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");

}


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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>");}

}


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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


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substr()


echo (substr($userString, 8));


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substr()


echo (substr($userString, 8,5));


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From the end of the string


echo (substr($userString, -10,10));


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How could this be useful?$userEmail=("[email protected]");

if (substr($userEmail, -2,2) == "uk"){echo ("UK customers pay £5 postage");}

else{echo ("You are not based in the UK, postage is £15");

}


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A further refinement$userEmail=("[email protected]");

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");}


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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


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What is echoed out?

$userString=("Hello everybody, it is a lovely day");

$delim = (" ");

$word = (strtok($userString, $delim));

echo $word;


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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”);


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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);


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strip_tags()

• Strip tags is very useful for stripping html tags from a string

$mytext = (“<h1>Hello World!</h1>”);

echo strip_tags ($mytext);


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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);


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Converting Case

• PHP provides 4 functions that manipulate the case of a string– strtoupper();– strtolower();– ucwords();– ucfirst();


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


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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 $myarray with two indexes.

• $myarray[0] = “Hello”;• $myarray[1] = “World”;


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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


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• 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

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> ");}

1. Get users text


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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;}


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3. Check Spelling• Create a function called checkSpelling

– the function will receive two arguments• $userText and $word

– use the explode function to split the $userText into an array called $userWord

– for each word in the array $userWord check against each word in the array $word

– if a match is found, copy the word to a variable called $correctUsersText without any formatting, else copy with bold formatting

– return $correctUsersText


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3. Check spellingfunction 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; }


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4. Output the spelling mistakes

• Create a function called display– accept one argument– echo the argument

function display ($txt){echo $txt;}


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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


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Spot the mistakes

$mystring = “Last updated 2001”

$mystring = substr_replace (mystring, “2007” -4, 4);


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Spot the mistakes$userEmail=([email protected]);

if (substr($userEmail, -2,2) == "uk"

echo ("UK customers pay £5 postage");

else

echo ("You are not based in the UK, postage is £15");


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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


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Summary Slide (cont.)

• Extracting specific text from a string• Splitting a string into new strings• Stripping HTML tags from strings• Replacing a portion of the string• Converting the Case of a string• Breaking strings into arrays


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Any Questions?

• Next Week– connecting to a SQL Server– creating a Database– selecting a Database– adding to a Database

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PHP – Working with Files and Strings