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--- rfc:array_column [2013/01/12 16:45] – Change "0-indexed number" to "integer key" ramsey
+++ rfc:array_column [2013/01/12 17:17] – Added Example #4 ramsey
@@ Line 143: / Line 143: @@
     [5342] => Jones
 )
+</code>
+=== Example #4: Mismatched columns ===
+With ''array_column()'' the relationship in finding the values of //**columnKey**// to //**indexKey**// is much like that of a SQL left join. All values of the //**columnKey**// are returned. When a corresponding //**indexKey**// cannot be found, the value will be keyed with an integer, starting from zero.
+The following examples will all use the same **$mismatchedColumns** array defined here:
+<code php>
+<?php
+$mismatchedColumns = array(
+    array(
+        'a' => 'foo',
+        'b' => 'bar',
+        'e' => 'baz'
+    ),
+    array(
+        'a' => 'qux',
+        'c' => 'quux',
+        'd' => 'corge'
+    ),
+    array(
+        'a' => 'grault',
+        'b' => 'garply',
+        'e' => 'waldo'
+    ),
+);
+</code>
+In this example, all rows contain an "a" key, but only two contain a "b" key. If we want to retrieve all "a" values and key them by "b" values, then ''array_column()'' behaves like this:
+<code php>
+<?php
+$foo = array_column($mismatchedColumns, 'a', 'b');
+$bar = array('bar' => 'foo', 'qux', 'garply' => 'grault');
+/*
+Both $foo and $bar contain values that look like this:
+Array
+(
+    [bar] => foo
+    [0] => qux
+    [garply] => grault
+)
+*/
+</code>
+However, if we want to retrieve all "b" values and key them by "a" values, we will only have two elements in the resulting array, since only two rows contain "b" values.
+<code php>
+// There is a corresponding "a" value for each "b" value
+print_r(array_column($mismatchedColumns, 'b', 'a'));
+/*
+Array
+(
+    [foo] => bar
+    [grault] => garply
+)
+*/
+// There are no corresponding "c" values for either "b" value
+print_r(array_column($mismatchedColumns, 'b', 'c'));
+/*
+Array
+(
+    [0] => bar
+    [1] => garply
+)
+*/
 </code>

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