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--- rfc:array_key_first_last_index [2015/12/07 17:58] – jbafford
+++ rfc:array_key_first_last_index [2016/01/01 20:11] – jbafford
@@ Line 19: / Line 19: @@
 array_key_last() returns the last key in an array.
-array_key_index() returns the key at a specified index (using a substr-like offset; positive starts from the beginning of the array; negative from the end).
+array_key_index() returns the key at a specified index (using a substr-like offset; greater-than or equal to zero starts from the beginning of the array; negative from the end).
+<code php>
+$arr ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4];
+$key = array_key_first($arr); //$key === 'a'
+$key = array_key_last($arr, $val); //$key === 'd', $val === 4
+$key = array_key_index($arr, 1); //$key === 'b'
+$key = array_key_index($arr, -2); //$key === 'c'
+$key = array_key_index($arr, 5, $val); //$key === NULL, $val is unchanged
+// Also works for numeric arrays
+$numeric = [1 => 1, 5 => 2, 2 => 3];
+$key = array_key_index($numeric, 0); //$key === 1
+$key = array_key_index($numeric, 1); //$key === 5
+$key = array_key_index($numeric, 2); //$key === 2
+</code>
 All three functions return the requested array key, or null if the requested array key is not found (an empty array, or an out-of-bounds index in the case of array_key_index). For convenience, each function also takes an optional $value parameter that, if provided and the specified index is found, will be set to contain the value at the specified index.