Functions & Arrays

Functions Functions offer the ability for programmers to group together program code that performs specific task or function into a single unit hat can be used repeatedly throughout a program. A function is defined by name and is invoked by using its name. Functions can accept data in the form of arguments and can return results. PHP has several built-in functions. However, the flexibility of PHP lies in the ability of programmers to create their own functions.

Basic PHP Functions abs() Function: Returns the absolute value of a number. sqrt( ) Function: Take the square root of a single numerical argument. round( ) Function: Returns the number rounded up or down to the nearest integer. is_number( ) Function: Testing whether a variable is a valid number or numeric string. It returns true or false.

Basic PHP Functions rand( ) Function. Generate a random number. date( ) Function. Determine the current date and time.

PHP Function Site

Functions Functions are defined using the function statement. function function_name(parameters, arguments) { command block } function printName($name) { echo (“ Your Name is ”); echo $name; echo (“ ”); } printName(“Bob”);

Functions Returning Results: function cube($number) { $result = $number * $number * $number; return $result; } $y = cube(3);

Functions with Optional Arguments function OutputLine($text, $size=3, $color = “black”) { echo “ $text } OutputLine(“Good Morning”); // use size 3 and color black OutputLine(“Good Morning”, 4); //use size 4 and color black OutputLine(“Good Morning”, 4, “red”); //use size 4 and color red

Using External Script Files PHP supports two different functions for including external script files in your scripts: –require( ) : produces a fatal error if the external script can’t be inserted. –include( ) : produces a warning if can’t insert the specified file.

Example: External File //header.php <? $time = date(‘H:I’); function Calc_perc($buy, $sell) { $per = (($sell - $buy) / $buy) * 100; return $per; } ?> Example <? include(“header.php”); $buy = 2.50; $sell = echo “ It is $time.”; echo “We have hammers on special for \$$sell!”; $markup = Calc_perc($buy, $sell); echo “ Our markup is only $markup%!!”; ?>

Arrays An array is a PHP variable that can hold multiple data values (like a list of numbers, names, or grocery items) Sequential Array: Keeps track of these data items by using sequential numbers. Associative Array: Keeps track of these data items by using character strings.

Advantages of Arrays Include a flexible number of list items. Can add and delete items on the fly. Examine each item more concisely. You can use looping constructs in combination with arrays to look at and operate on each array item in a very concise manner. Use special array operators and functions. Built-in array operators and functions to do things such as count the number of items, sum the items, and sort the array.

Examples of Sequential Arrays $students = array(‘Johnson’, ‘Jackson’,’Jefferson’); $grades = array(66, 72, 89); echo “The first student is $student[0]”; echo “The second student is $student[1]”; $average = ($grades[0] + grades[1] + grades[2])/3; echo “The average of the grades is $average”; $sum = 0; for (i=0; i < count(grades); i++) $sum += $grades[i]; average = $sum/count(grades);

Use of “foreach” foreach ($student as $item) { echo (“$item”); } Output: Johnson Jackson Jefferson

Array Functions array_shift( ) :Remove an item from the beginning of an array. array_unshift( ) : Add an item to the beginning of an array. array_pop( ) : Remove an item from the end of an array. array_push( ) : Add an item to the end of an array.

Array Functions max( ) and min( ) functions : Determine largest and smallest numerical value in an array, respectively. array_sum( ) : Sum numerical values in the array. sort( ) : Reorder the items in numerical or alphabetical order.

Associative Arrays A string value index is used to look up or provide a cross-reference to the data value. Example: –$instructors = array(“Science” => “Smith”, “Math” => “Jones”, “English” => “Jacks”); echo “Instructor of Science is $instructors(‘Science’).” Output: Instructor of Science is Smith.

Associative Arrays foreach ($instructors as $subject => $teacher) { echo “Subject is $subject, teacher is $teacher ”; } Output: Subject is Science, teacher is Smith Subject is Math, teacher is Jones Subject is English, teacher is Jacks

Associative Arrays Adding an Associative Array Item: $instructors[“Language”] = “Pearson”; Deleting an Associative Array Item: unset($instructors[“Science”]); Verifying an Item’s Existence: if (isset($instructors[“Science”])) { echo (“Science is in the list.”); } else { echo (“Science is NOT in the list.”); }

Associative Arrays asort( ) : Sort an associative array by the values of the array while maintaining the relationship between indices and values. ksort( ) : Sort an associative array by the indices of the array while maintaining the relationship between indices and values.

Multidimensional Arrays Two-dimensional is a table: Example: Part No. Part Name Count Price AC10 Hammer AC11 Wrench $inventory = array ( ‘AC10’=>array(‘part’=>’Hammer’,’Count’=>122, ‘Price’=>12.50), ‘AC11’=>array(‘part’=>’Wrench’,’Count’=>5, ‘Price’=>5.50)); echo $inventory[‘AC10’][‘part’]; Output: Hammer