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Functions & Arrays
| Date post: | 18-Dec-2015 |
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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.
Functions
• Functions are defined using the function statement.function function_name(parameters, arguments) {
command block }
function printName($name) {
echo (“<HR> Your Name is <B><I>”);
echo $name;
echo (“</B></I><HR>”);
}
printName(“Bob”);
Functions
• Returning Results:function cube($number) {
$result = $number * $number * $number;
return $result;
}
$y = cube(3);
Functions with Optional Arguments
function OutputLine($text, $size=3, $color = “black”) { echo “<font color = $color size = $size> $text </font>}
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; }?>
<html><head><title>Example</title></head><body><? include(“header.php”); $buy = 2.50; $sell = 10.00 echo “<br> It is $time.”; echo “We have hammers on special for \$$sell!”; $markup = Calc_perc($buy, $sell); echo “<br> Our markup is only $markup%!!”; ?></body></html>
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<br>”; }
Output:
Subject is Science, teacher is SmithSubject is Math, teacher is JonesSubject 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 PriceAC10 Hammer 122 12.50AC11 Wrench 5 5.00
$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
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