PHP Functions & Arrays

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Basic Syntax function name(){ } function hello() { echo “Hello World!”; } hello();

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Returning Values function hello(){ return “Hello World!”; } $txt = hello(); echo hello();

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Returning Values function hello(){ echo “Hello $who”; if ($who == “World”) { return; } echo “, how are you?”; } hello (“World”); //Displays “Hello World” hello (“Reader”); //Displays “Hello Reader, how are you?”

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Returning Values function &query($sql) { $result= mysql_query($sql); return $result; } //The following is incorrect and will cause PHP to emit a notice when called. function &getHello() { return “Hello World”; } //This will also cause the warning to be issued when called function &test() { echo „This is a test‟; }

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Variable Scope • Threevariable scopes exist: • Global • Function • Class

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Variable Scope, cont’d $a= “Hello World”; function hello() { $a = “Hello Reader”; $b = “How are you?”; } hello (); echo $a; //Will output Hello World echo $b; //Will emit a warning

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Variable Scope, cont’d $a= “Hello”; $b = “World”; function hello() { global $a, $b; echo “$a $b”; } hello (); //Displays Hello World

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Variable Scope, cont’d $a= “Hello”; $b = “World”; function hello() { echo $GLOBALS[„a‟].‟ „.$GLOBALS[„b‟]; } hello (); //Displays Hello World

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Variable-Length Argument Lists functionhello() { if (func_num_args() > 0) { $arg = func_get_arg(0); echo “Hello $arg”; } else { echo ”Hello World”; } } hello(“Reader);

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Variable-Length Argument Lists functioncountAll($arg1){ if (func_num_args() == 0) { die(“You need to specify at least one argument”); } else { $args = func_get_args(); array_shift($args); $count = strlen($arg1); foreach ($args as $arg) { $count += strlen($arg); } } return $count; } echo countAll(“apple”,”pear”, “plum”);

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Passing Arguments byReference function countAll(&$count){ if (func_num_args() == 0) { die(“You need to specify at least one argument”); } else { $args = func_get_args(); array_shift($args); $count = strlen($arg1); foreach ($args as $arg) { $count += strlen($arg); } } } $count = 0; countAll($count, “apple”,”pear”, “plum”); //count now equals 13

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Arrays

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Array Basics $a =array (10, 20, 30); $a = array (‟a‟ => 10, ‟b‟ => 20, ‟cee‟ => 30); $a = array (5 => 1, 3 => 2, 1 => 3,); $a = array();

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Array Basics $x[] =10; $x[‟aa‟] = 11; echo $x[0]; // Outputs 10

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Printing Arrays • PHPprovides two functions that can be used to output a variable’s value recursively • print_r() • var_dump().

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Enumerative vs Associative •Arrays can be roughly divided in two categories: enumerative and associative. • Enumerative arrays are indexed using only numerical indexes • Associative arrays(sometimes referred to as dictionaries) allow the association of an arbitrary key to every element.

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Enumerative vs Associative,cont’d When an element is added to an array without specifying a key, PHP automatically assigns a numeric one that is equal to the greatest numeric key already in existence in the array, plus one: $a = array (2 => 5); $a[] = ‟a‟; // This will have a key of 3 $a = array (‟4‟ => 5, ‟a‟ => ‟b‟); $a[] = 44; // This will have a key of 5

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Array keys arecase-sensitive, but type insensitive. Thus, the key ’A’ is different from the key ’a’, but the keys ’1’ and 1 are the same. However, the conversion is only applied if a string key contains the traditional decimal representation of a number; thus, for example, the key ’01’ is not the same as the key 1. NOTE WELL

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Multi-dimensional Arrays $array =array(); $array[] = array(‟foo‟, ‟bar‟); $array[] = array(‟baz‟, ‟bat‟); echo $array[0][1] . $array[1][0]; //output is barbaz

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Unravelling Arrays $sql ="SELECT user_first, user_last, lst_log FROM users"; $result = mysql_query($sql); while (list($first, $last, $last_login) = mysql_fetch_row($result)) { echo "$last, $first - Last Login: $last_login"; }

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array(6) { [0]=> Array Operations int(1) [1]=> int(2) [2]=> $a= array (1, 2, 3); int(3) $b = array (‟a‟ => 1, ‟b‟ => 2, ‟c‟ => 3); ["a"]=> var_dump ($a + $b); int(1) ["b"]=> int(2) ["c"]=> int(3) }

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Array Operations, cont’d array(4){ [0]=> int(1) $a = array (1, 2, 3); [1]=> $b = array (‟a‟ => 1, 2, 3); int(2) var_dump ($a + $b); [2]=> int(3) ["a"]=> int(1) }

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Comparing Arrays $a =array (1, 2, 3); $b = array (1 => 2, 2 => 3, 0 => 1); $c = array (‟a‟ => 1, ‟b‟ => 2, ‟c‟ => 3); var_dump ($a == $b); // True var_dump ($a === $b); // False var_dump ($a == $c); // False var_dump ($a === $c); // False

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Comparing Arrays, cont’d $a= array (1, 2, 3); $b = array (1 => 2, 2 => 3, 0 => 1); var_dump ($a != $b); // False var_dump ($a !== $b); // True

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Counting, Searching andDeleting Elements $a = array (1, 2, 4); $b = array(); $c = 10; echo count ($a); // Outputs 3 echo count ($b); // Outputs 0 echo count ($c); // Outputs 1

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Counting, Searching andDeleting Elements, cont’d $a = array (‟a‟ => 1, ‟b‟ => 2); echo isset ($a[‟a‟]); // True echo isset ($a[‟c‟]); // False $a = array (‟a‟ => NULL, ‟b‟ => 2); echo isset ($a[‟a‟]); // False

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Counting, Searching andDeleting Elements, cont’d $a = array (‟a‟ => NULL, ‟b‟ => 2); echo array_key_exists (‟a‟, $a); // True $a = array (‟a‟ => NULL, ‟b‟ => 2); echo in_array (2, $a); // True

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Counting, Searching andDeleting Elements, cont’d $a = array (‟a‟ => NULL, ‟b‟ => 2); unset ($a[‟b‟]); echo in_array ($a, 2); // False

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Flipping and Reversing $a= array (‟a‟, ‟b‟, ‟c‟); array(3) {{ array(3) ["a"]=> [0]=> int(0) string(1) "c" ["b"]=> [1]=> int(1) string(1) "b" ["c"]=> ["x"]=> int(2) string(1) "a" var_dump (array_flip ($a)); $a = array (‟x‟ => ‟a‟, 10 => ‟b‟, ‟c‟); var_dump (array_reverse ($a)); }}

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Array Iteration • Oneof the most common operations you will perform with arrays • PHP arrays require a set of functionality that matches their flexibility • “normal” looping structures cannot cope with the fact that array keys do not need to be continuous $a = array (‟a‟ => 10, 10 => 20, ‟c‟ => 30);

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Array Iteration: ArrayPointer $array = array(‟foo‟ => ‟bar‟, ‟baz‟, ‟bat‟ => 2); function displayArray(&$array) { reset($array); while (key($array) !== null) { echo key($array) .": " .current($array) . PHP_EOL; next($array); } }

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Array Iteration: foreach $array= array(‟foo‟, ‟bar‟, ‟baz‟); foreach ($array as $key => $value) { echo "$key: $value"; }

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array(2) { ["internal"]=> Passive Iteration &array(3){ [0]=> string(3) "RSS" [1]=> function setCase(&$value, &$key) string(4) "HTML" { [2]=> string(3) "XML" $value = strtoupper($value); } } ["custom"]=> $type = array(‟internal‟, ‟custom‟); &array(2) { $output_formats[] = array(‟rss‟, ‟html‟, ‟xml‟); [0]=> $output_formats[] = array(‟csv‟, ‟json‟); string(3) "CSV" $map = array_combine($type, $output_formats); [1]=> array_walk_recursive($map, ‟setCase‟); string(4) "JSON" } var_dump($map); }

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Sorting Arrays: sort() $array= array(‟a‟ => ‟foo‟, ‟b‟ => ‟bar‟, ‟c‟ => ‟baz‟); sort($array); array(3) { [0]=> var_dump($array); string(3) "bar" [1]=> string(3) "baz" [2]=> string(3) "foo" }

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Sorting Arrays: asort() $array= array(‟a‟ => ‟foo‟, ‟b‟ => ‟bar‟, ‟c‟ => ‟baz‟); asort($array); var_dump($array); array(3) { ["b"]=> string(3) "bar" ["c"]=> string(3) "baz" ["a"]=> string(3) "foo“ }

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Sorting Arrays SORT_REGULAR Compare itemsas they appear in the array, without performing any kind of conversion. This is the default behaviour. SORT_NUMERIC Convert each element to a numeric value for sorting purposes. SORT_STRING Compare all elements as strings.

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Sorting Arrays: natsort() $array= array(‟10t‟, ‟2t‟, ‟3t‟); natsort($array); array(3) { [1]=> var_dump($array); string(2) "2t" [2]=> string(2) "3t" [0]=> string(3) "10t" }

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Anti-Sorting: shuffle() $cards =array (1, 2, 3, 4); array(4) { [0]=> shuffle($cards); int(4) var_dump($cards); [1]=> int(1) [2]=> int(2) [3]=> int(3) }

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Anti-Sorting: array_keys() $cards =array (‟a‟ => 10, ‟b‟ => 12, ‟c‟ => 13); $keys = array_keys ($cards); shuffle($keys); foreach ($keys as $v) { echo $v . " - " . $cards[$v] . "n"; }

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Anti-Sorting: array_rand() $cards =array (‟a‟ => 10, ‟b‟ => 12, ‟c‟ =>array(2) { { 13); array(3) $keys = array_rand ($cards, 2); ["a"]=> [0]=> int(10) string(1) "a" ["b"]=> [1]=> var_dump($keys); int(12) string(1) "b" var_dump($cards); ["c"]=> } int(13) }

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Arrays as Stacks,Queues and Sets $stack = array(); array_push($stack, ‟bar‟, ‟baz‟); var_dump($stack); $last_in = array_pop($stack); var_dump($last_in, $stack);

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Arrays as Stacks,Queues and Sets array(2) { [0]=> $queue = array(‟qux‟, ‟bar‟, ‟baz‟); string(3) "bar" [1]=> $first_element = array_shift($queue); var_dump($queue); string(3) "baz" } array(3) { array_unshift($queue, ‟foo‟); [0]=> string(3) "foo" var_dump($queue); [1]=> string(3) "bar" [2]=> string(3) "baz" }

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Set Functionality $a =array (1, 2, 3); $b = array (1, 3, 4); var_dump (array_diff ($a, $b)); var_dump (array_intersect ($a, $b));

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Functions & Arrays