Chapter 3 Array

Indexed Versus Associative Arrays There are two kinds of arrays in PHP: indexed and associative. The keys of an indexed array are integers, beginning at 0. Indexed arrays are used when you identify things by their position. Associative arrays have strings as keys and behave more like two-column tables. The first column is the key, which is used to access the value.

Creating Arrays 1.) Integer-Indexed Array Numerically indexed arrays can be created to start at any index value There are two ways in creating Array in PHP: formal and informal array declaration methodologies.

Creating Arrays 1.) Integer-Indexed Array A.) Informal array declaration Individual elements of a PHP array are referenced by denoting the element between a pair of square brackets, like this: $state[0] = “Norton"; $state[1] = “NUM"; $state[2] = “RUPP";... $state[49] = “IFL"; You can then display the first element of the array $state like this: echo $state[0];

1.) Integer-Indexed Array B.) Formal array declaration PHP provides the array( ) language construct that creates arrays. The following examples show how arrays of integers and strings can be constructed and assigned to variables for later use: $numbers = array(5, 4, 3, 2, 1); $words = array("Web", "Database", "Applications"); // Print the third element from the array // of integers: 3 echo $numbers[2]; // Print the first element from the array // of strings: "Web“ echo $words[0]; Creating Arrays

2.) Associative Array A.) Informal array declaration Individual elements of a PHP array are referenced by denoting the element between a pair of square brackets, like this: $state["Delaware"] = "December 7, 1787"; $state["Pennsylvania"] = "December 12, 1787"; $state["New Jersey"] = "December 18, 1787";... $state["Hawaii"] = "August 21, 1959"; You can then display the first element of the array $state like this: echo $state["Delaware"] ;

1.) Associative Array B.) Formal array declaration PHP provides the array( ) language construct that creates arrays. The following examples show how arrays of integers and strings can be constructed and assigned to variables for later use: $array = array("first"=>1, "second"=>2, "third"=>3); // Echo out the second element: prints "2“ echo $array["second"]; $languages = array ("Spain" => "Spanish", "Ireland" => "Gaelic", "United States" => "English"); Creating Arrays

Heterogeneous arrays The values that can be stored in a single PHP array don't have to be of the same type. PHP arrays can contain heterogeneous values $mixedBag = array("cat", 42, 8.5, false); var_dump($mixedBag); Print_r($mixedBag); // var_dump output: array(4) { [0]=> string(3) "cat" [1]=> int(42) [2]=> float(8.5) [3]=> bool(false) } // print_r output: Array ( [0] => cat [1] => 42 [2] => 8.5 [3] => )

Multidimensional arrays PHP arrays can also hold other arrays creating multidimensional arrays. Multi-dimensional arrays A two dimensional array <?php // A two dimensional array using integer indexes $planets = array(array("Mercury", 0.39, 0.38), array("Venus", 0.72, 0.95), array("Earth", 1.0, 1.0), array("Mars", 1.52, 0.53) ); // prints "Earth" print $planets[2][0] ?>

Using foreach Loops with Arrays the easiest way to iterate through—or traverse—an array is using the foreach statement The foreach statement has two forms: foreach(array_expression as $value) statement foreach(array_expression as $key => $value) statement The first form assigns the value from the element to a variable identified with the as keyword; the second form assigns both the key and the value to a pair of variables.

Example of the first form <?php // Construct an array of integers $lengths = array(0, 107, 202, 400, 475); // Convert an array of centimeter lengths to inches foreach($lengths as $cm){ $inch = $cm / 2.54; echo "$cm centimeters = $inch inches\n"; } ?> The example iterates through the array in the same order it was created: 0 centimeters = 0 inches 107 centimeters = inches 202 centimeters = inches 400 centimeters = inches 475 centimeters = inches

Example of the second form <?php $sounds = array("cow"=>"moo", "dog"=>"woof", "pig"=>"oink", "duck"=>"quack"); foreach ($sounds as $animal => $sound) { echo " Old MacDonald had a farm EIEIO"; echo " And on that farm he had a $animal EIEIO"; echo " With a $sound-$sound here"; echo " And a $sound-$sound there"; echo " Here a $sound, there a $sound"; echo " Everywhere a $sound-$sound"; } ?>

Some Useful Functions current( ): returns the value pointed to by the array's internal index. each( ): returns an array that holds the index key and the value of the current element. each( ) returns has four elements: two that hold the key, accessed by the numeric index 0 and the associative key key; and two that hold the value, accessed by the numeric index 1 and the associative key value. end( ): returns the value in last index next( ): returns the value in next index prev( ): returns the value in previous index reset( ): returns array's internal pointer to the first element key( ): returns the key in current index

Some Useful Functions(cont) The list( ) function isn't really a function, but a language construct that assigns multiple variables from an array expression: list($var1, $var2,...) = array_expression <?php $sounds = array ("pig"=>"ouk", "cow"=>"moo", "duck"=>"quack", "dog"=>"woof"); while (list($animal, $sound) = each($sounds)){ echo " Old MacDonald had a farm EIEIO"; echo " And on that farm he had a $animal EIEIO"; echo " With a $sound-$sound here"; echo " And a $sound-$sound there"; echo " Here a $sound, there a $sound"; echo " Everywhere a $sound-$sound"; } ?>

Basic Array Functions Counting elements in Array integer count(mixed var) Finding maximun and minimum values in Array number max(array numbers) number min(array numbers) Finding values in array boolean in_array(mixed needle, array haystack [, boolean strict]) The in_array( ) function returns true if an array haystack contains a specific value needle: $smallPrimes = array(3, 5, 7, 11, 13, 17, 19, 23, 29); if (in_array(19, $smallPrimes)) echo "19 is a small prime number"; // Always printed

Basic Array Functions(Cont.) Finding values in array mixed array_search(mixed needle, array haystack [, boolean strict]) The array_search( ) function works the same way as the in_array( ) function, except the key of the matching value needle is returned rather than the Boolean value true: $measure = array("inch"=>1, "foot"=>12, "yard"=>36); // prints "foot“ echo array_search(12, $measure); Reordering elements in array array array_reverse(array source [, bool preserve_keys]) $count = array("zero", "one", "two", "three"); $countdown = array_reverse($count); //setting the second optional argument. count = array("zero", "one", "two", "three"); $countdown = array_reverse($count, true); print_r($countdown);

Basic Array Functions(Cont.) Sorting Integer-Indexed Arrays on values sort(array subject [, integer sort_flag]) rsort(array subject [, integer sort_flag]) $numbers = array(24, 19, 3, 16, 56, 8, 171); sort($numbers); foreach($numbers as $n) echo $n. " "; $numbers = array(24, 19, 3, 16, 56, 8, 171); rsort($numbers); foreach($numbers as $n) echo $n. " ";

Basic Array Functions(Cont.) Sorting Associative Arrays on values asort(array subject [, integer sort_flag]) arsort(array subject [, integer sort_flag]) $map = array("o"=>"kk", "e"=>"zz", "z"=>"hh", "a"=>"rr"); asort($map);print_r($map); Sorting on keys integer ksort(array subject [, integer sort_flag]) integer krsort(array subject [, integer sort_flag])

The end of Chapter 2 Thanks for your paying attention