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--- en:create:array [09.11.2014 15:18] – alexander.ritter
+++ en:create:array [18.11.2020 17:30] (current) – [Arrays] sophia.schauer
@@ Line 11: / Line 11: @@
 // create an array
 $a = array('one', 'two', 'three');
+</code>
+Instead of the notation ''array()'' a short notation with square brackets is also possible. The function is identical.
+<code php>
+// Create an array with square brackets
+$a = ['one', 'two', 'three'];
 </code>
@@ Line 37: / Line 44: @@
 <code php>
-$a = array()
+$a = array();
 for ($i=0; $i<10; $i++) {
   $a[] = $i + 1;
@@ Line 171: / Line 178: @@
 ''array_merge()'' (join) and ''array_intersect()'' (intersection) are similarly useful.
+===== Associative Arrays =====
+Normal arrays are simply a list of elements. Each element has a unique position, marked by the index (''0'', ''1'', u.s.w). The index is also known as //key//.
+You create an associative array by explicitly setting the key. For assigning values to keys, PHP uses the characters ''%%=>%%''. You __may__ use the well known index as a key -- arrays ''$a'' and ''$b'' in the subsequent PHP code are equivalent.
+<code php>
+$a = array(
+  'one',
+  'two',
+  'three'
+);
+$b = array(
+=> 'one',
+=> 'two',
+=> 'three'
+);
+</code>
+Yet, keys are not limited to numbers -- you may as well use strings. The next array defines the correct answers for a row of knowledge questions (question type "selection").
+<code php>
+$c = array(
+  'AB01' => 2,
+  'AB02' => 1,
+  'BB01' => 5
+);
+</code>
+To access thee element of an associative array, just specify the key in square brackets:
+<code php>
+$x = $c['AB01'];
+// also possible
+$key = 'AB01';
+$x = $c[$key];
+</code>
+When working with associative arrays, the PHP internal function ''[[http://php.net/manual/en/function.array-keys.php|array_keys()]]'' as well as the FOR loop ''[[http://php.net/manual/en/control-structures.foreach.php|foreach]]'' are very helpful. The following PHP code checks, if a correct answer was given to multiple quesitons ([[:en:create:points|Count Points for Answers]]).
+<code php>
+$c = array(
+  'AB01' => 2,
+  'AB02' => 1,
+  'BB01' => 5
+);
+foreach ($c as $label=>$correct) {
+  if (value($label) == $correct) {
+    html('<p style="color: green">The answer to '.$label.' is correct.</p>');
+  } else {
+    html('<p style="color: red">The answer to '.$label.' is wrong.</p>');
+  }
+}
+</code>
+Using ''array_keys()'' also allows regular FOR loops:
+<code php>
+$c = array(
+  'AB01' => 2,
+  'AB02' => 1,
+  'BB01' => 5
+);
+$fragen = array_keys($c);
+for ($i=0; $i<count($fragen); $i++) {
+  $label = $fragen[$i];
+  $correct = $c[$label];
+  if (value($label) == $correct) {
+    html('<p style="color: green">The answer to '.$label.' is correct.</p>');
+  } else {
+    html('<p style="color: red">The answer to '.$label.' is wrong.</p>');
+  }
+}
+</code>
 ===== Further Array Functions =====
 There is a whole range of further commands used for arrays. You can find a complete list in the official [[http://de3.php.net/manual/en/ref.array.php|PHP Manual: Array Functions]].