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Chapter 3 Array

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.

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Chapter 3 Array

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  1. Chapter 3 Array

  2. 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.

  3. 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.

  4. 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];

  5. Creating Arrays 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];

  6. 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"] ;

  7. Creating Arrays 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");

  8. 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] => )

  9. Multidimensional arrays • PHP arrays can also hold other arrays creating multidimensional arrays. <html><head> <title>Multi-dimensional arrays</title></head> <body bgcolor="#ffffff"> <h2>A two dimensional array</h2> <?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] ?>

  10. 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.

  11. 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 = 42.125984251969 inches 202 centimeters = 79.527559055118 inches 400 centimeters = 157.48031496063 inches 475 centimeters = 193.87755102041 inches

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

  13. 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

  14. 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 "<p>Old MacDonald had a farm EIEIO"; echo "<br>And on that farm he had a $animal EIEIO"; echo "<br>With a $sound-$sound here"; echo "<br>And a $sound-$sound there"; echo "<br>Here a $sound, there a $sound"; echo "<br>Everywhere a $sound-$sound"; } ?>

  15. 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

  16. 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);

  17. 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 . " ";

  18. 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])

  19. The end of Chapter 2 Thanks for your paying attention

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