LIS651 lecture 3 functions and arrays

Thomas Krichel 2010-02-11 LIS651 lecture 3functions and arrays

today • more string functions • general function desciption • more number functions • arrays • the foreach() {} statement

string functions • There are a long list of string functions in the PHP reference manual. When you work with text, you should look at those string functions at http://www.php.net/manual/en/ref.strings.php • Working with text is particularly important when checking the input of users into your form. • I am looking at just a few of examples here. You really need to read the reference to see what is available.

trim() • trim(string) removes the whitespace at the beginning and the end of the string string. It returns the transformed string. $input=" Festbock "; $output=trim($input); print "|$output|"; // prints: |Festbock| • whitespace is any of the following characters • the blank character • the newline • the carriage return • the tabulation character

strlen() • strlen(string) returns the length of the string string. $zip=trim($_POST['zipcode']); $zip_length=strlen($zip); print $zip_length; // hopefully, prints 5

strip_tags() • strip_tags(string) removes HTML tags from the string string $input="<b>But</b>weiser"; print strip_tags($input); // prints: Butweiser $in="<a href=\"http://porn.com\"><img src=\"http://porn.com/ad.gif\"/></a>"; print strip_tags($in); // prints nothing, hurray!

htmlspecialchars() • htmlspecialchars(string) makes XML entities out of XML special characters in the string string. <,>,&, and " are transformed. It returns the transformed string. $in="What does the <div> element do?"; print htmlspecialchars($in); // prints: What does the <div> element do? • Using htmlspecialchars() is considered to be good security because it prevents injection of HTML and especially its <script> element.

substr() • substr( string , start , offset) returns the substring of a string string starting at position start, with length offset. $string=“I like beer.”; $sub=substr($string, 2, 4); print $sub; // prints “like”

documentation: description string trim ( string $str [, string $charlist ] ) • here "string" at the beginning tells us that the function returns a variable of type string. • The name of the function is written in bold. • Then comes the parenthesis. It encloses the arguments. • Anything that is optional is enclosed in square brackets. Don't put the square bracket in the function call.

argument list • string $str [, string $charlist ] • This argument list suggests • that you have to give a first argument that is a string (or will be converted to it) • that there is an optional argument that also is a string • arguments are separated by comma. • The arguments are described in the parameters section.

return value • There is a section in the description for the returned value. • You will be told what type. • You will be told what it means.

more number functions • abs() calculates the absolute value print abs(-3) // prints: 3 print abs(3) // prints: 3 • max() and min() return maximum and minimum print min(2,3) // prints: 2 • rand( min , max ) returns a random integer between the integers min and max, included. • The list of functions that use numbers is http://php.net/manual/en/ref.math.php

variable types • Variables in PHP have types. You can check for types is_numeric() is_string() is_int() is_float() • They all return a Boolean value. • They can be used to check the nature of a variable.

arrays • The variables we have looked at up until now are scalars. They only contain one piece of data. • Arrays are variables that can contain more than one piece of data. • For example, a six pack in conveniently represented as an array of cans of beer. • For another example, a class is a group of people, each having a name, a social security number, etc.

numeric arrays • An numeric array has key value pairs where the keys are numbers. $good_beers[0]="Baltika 8"; $good_beers[1]="Bruch Festbock"; • or as follows $lousy_beers=array("Miller Lite", "Sam Adams", "Budweiser"); print $lousy_beers[0]; // prints: Miller Lite print $lousy_beers[2]; // prints: Budweiser

keeping count in numeric arrays • For numeric arrays, you can add members very simple without keeping track of number. $beers=array("Karlsberg", "Bruch") ; $beers[]="Budweiser"; // $beer now has Karlberg, Bruch and Budweiser print count($beers) ; // prints 3

string arrays • Sometimes you need data structured by a string. For example for a price list. $price['Grosswald Export']=1.45; $price['Bruch Festbock']=1.74; // the array $price has strings as keys • An equivalent way to declare this is $price=array('Grosswald Export' => 1.45, 'Bruch Festbock' => 1.74);

array functions • There is a very large number of array functions. They are described in the array function reference. http://www.php.net/manual/en/ref.array.php • Now we are just looking at some examples.

count() • count() returns the size of an array $price['Grosswald Export']=1.45; $price['Bruch Festbock']=1.74; $product_number=count($price); print "We have $product_number products for you today."; // prints: We have 2 products for you today.

unset() • This can be used to unset an element $beers_drunk('Amstel' => 'good', 'Miller' =>'ok', 'Budweiser'=>'lousy'); unset($beers_drunk('Amstel'); • Now the array $beers_drunk only has two elements.

foreach() {} loop, numeric array • The foreach loop loops over arrays. You use it as foreach($array as $element). • The array $array is the array you are looping through. • Each time you reach a new element, the current element is placed in $element.

a foreach() example $bottles=array('Amstel', 'Karlsberg', 'Sam Adams'); foreach($bottles as $beer) { print "Thomas has a $beer,\n"; } // prints: // "Thomas has a Amstel, // Thomas has a Karlsberg, // Thomas has a Sam Adams,"

foreach() loop, string array • The foreach loop loops over arrays. You use it as foreach( $array as $key => $value ). • The array $array is the array you are looping through. • Each time you reach a new element, the current key is placed in $key and the value in $value.

another foreach() example • Recall the $price string array. • Another example illustrates print "<table caption=\"price list\">\n"; foreach ($price as $item => $euro_amount) { print "<tr><td>$item</td>\n"; print "<td>€$euro_amount</td></tr>\n"; } print "</table>"; • This prints the full price list. But it could also do the whole form. This is fabulous!

foreach() example from the form • $_GET is an array. You can loop through it. foreach($_GET as $control => $value) { print “you set $control to $value<br/>\n”; }

the well-aligned price table $l_r=array('left','right'); $count=0; // counter of elements printed print "<table caption=\"price list\">\n"; foreach ($price as $item => $euro_amount) { print "<tr><td align=\"$l_r[$count % 2]\""; print "$item"; $count++; print "</td>\n<td align=$l_r[$count % 2]\"> €$euro_amount</td></tr>\n"; $count++; }

print "</table>\n"; // This produces something like // <table caption="price list"> // <tr><td align="left">Grosswald Export</td> // <td align="right">€1.45</td></tr> // <tr><td align="left">Bruch Festbock</td> // <td align="right"'>€1.74</td></tr> // </table>

Thank you for your attention! Please switch off machines b4 leaving! http://openlib.org/home/krichel

LIS651 lecture 3 functions and arrays