rfc:array_key_first_last_index

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rfc:array_key_first_last_index [2015/12/07 17:58] – jbaffordrfc:array_key_first_last_index [2016/01/01 20:19] – jbafford
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 ===== Proposal ===== ===== Proposal =====
 +Arrays in php are ordered maps, but there is no convenient way to 
 +
 array_key_first() returns the first key in an array. array_key_first() returns the first key in an array.
  
 array_key_last() returns the last key in an array. 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. 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.
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 With the reference implementation provided below, array_key_first() and array_key_last() directly retrieve the array key from the underlying hash (by setting a local hash pointer to the start/end of the array and retrieving the key for that index). By necessity, array_key_index() iterates through the keys, but does so in C code, rather than in PHP code. With the reference implementation provided below, array_key_first() and array_key_last() directly retrieve the array key from the underlying hash (by setting a local hash pointer to the start/end of the array and retrieving the key for that index). By necessity, array_key_index() iterates through the keys, but does so in C code, rather than in PHP code.
 +
 +In the proposed PR implementing this functionality (see below), array_key_first() and array_key_last() are implemented in terms of array_key_index(); array_key_index() exists a a consequence and extension of generalizing the common code between array_key_first() and array_key_last().
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
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   - a link to the git commit(s)   - a link to the git commit(s)
   - a link to the PHP manual entry for the feature   - a link to the PHP manual entry for the feature
- 
rfc/array_key_first_last_index.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1

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