array_key_last

For PHP <= 7.3.0 :if (! function_exists("array_key_last")) {    function array_key_last($array) {        if (!is_array($array) || empty($array)) {            return NULL;        }                return array_keys($array)[count($array)-1];    }}

For those who loves tested candies;<?phpfunction array_key_last(array $array) {    // 100000 iters: ~0.068 secs    return key(array_slice($array, -1));    // 100000 iters: ~0.070 secs    return key(array_reverse($array));    // 100000 iters: ~0.088 secs    return array_keys($array)[count($array) - 1] ?? null;}?>

Try to beat this polyfill in terms of performance!<?phpif( !function_exists('array_key_last') ) {    function array_key_last(array $array) {        if( !empty($array) ) return key(array_slice($array, -1, 1, true));    }}// Bonusif (!function_exists('array_key_first')) {    function array_key_first(array $arr) {        foreach($arr as $key => $unused) return $key;    }}?>

https://www.php.net/manual/fr/function.array-key-last.php#123950did return the first key of my array only:"array_keys($array)[count($array) - 1] ?? null" worksI hope the example is fine for everyone else.My array is:[            new NameExpression('d', 0),            new NameExpression('f', 0),            new NameExpression('g', 0),]

<?php     // PHP >= 7    function _array_key_last(array $array){        return (!empty($array)) ? array_keys($array)[count($array)-1] : null;    }    var_dump(_array_key_last(['PHP', 'Javascript', 'Python'])); // 2 ?>

// if : php ver < 7 // array_key_last $arr = array('1'=>'bear1','2'=>array('22'=>'bear22'),'3'=>'bear3');echo end(array_keys($arr));// result : 3

Notice!$a = array(    1 => 1,    0 => 0);echo (array_key_last($a)); // output: "0", not "1"

For PHP < 7.3.0 :Will work for any type of array<?phpif ( ! function_exists( 'array_key_last' ) ) {    /**     * Polyfill for array_key_last() function added in PHP 7.3.     *     * Get the last key of the given array without affecting     * the internal array pointer.     *     * @param array $array An array     *     * @return mixed The last key of array if the array is not empty; NULL otherwise.     */    function array_key_last( $array ) {        $key = NULL;        if ( is_array( $array ) ) {            end( $array );            $key = key( $array );        }        return $key;    }}?>

Now that we have this function, where we once used...<?php$idxLast = count($arr) - 1;?>we can now optimize code speed by using...<?php$idxLast = (array_key_last($arr) ?? 0);?>Use-cases include lots of looping and control-structures.If you do not know ahead of time that the array is numerically indexed, and that it could possibly be associative...safer/faster to stick with count().

This polyfill works for PHP 5.6+. It is a slight modification of "wes at nospam dot example dot org"'s example:<?php    if( !function_exists('array_key_first') ) {        function array_key_first(array $array) {            if( $array === [] ) { return NULL; }            foreach($array as $key => $_) { return $key; }        }    }    if( !function_exists('array_key_last') ) {        function array_key_last(array $array) {            if( $array === [] ) { return null; }                         // the last 2 args to array_slice are crucial            return array_key_first(array_slice($array, -1, null, true));        }    }

Here come my benchmark, and return key(array_slice($array, -1));is the my best answer for a polyfill.<?phpfunction array_key_last_1(array $array) {    // assert(!empty($array));    return key(array_slice($array, -1));}function array_key_last_2(array $array) {    return key(array_slice($array, -1, 1, true));}function array_key_last_3(array $array) {    return key(array_reverse($array));}function array_key_last_4(array $array) {    return array_keys($array)[count($array) - 1] ?? null;}function array_key_last_5(array $array) {    return array_keys($array)[count($array) - 1] ?? null;}function array_key_last_6(array $array) {    $copy = array_keys($array);    return end($copy);}$result = array();$array = range(0, 1000000);for($i=1; $i < 7;$i++) {  $callback = 'array_key_last_' . $i;  $before = microtime(true);  call_user_func_array($callback, array($array));  $after = microtime(true);  $time = ($after-$before);  $result[$callback] = $time;}asort($result);foreach ($result as $key => $value) {    echo '[' . $key . ']' . $value . " sec" . PHP_EOL;}

Correct polyfill (one that doesn't make copies of arrays, and that doesn't make use of the IAP) is:<?phpif(!function_exists('array_key_first')){    function array_key_first(array $array){        if($array === []){            return NULL;        }        foreach($array as $key => $_) return $key;    }}if(!function_exists('array_key_last')){    function array_key_last(array $array){        if($array === []){            return NULL;        }        return array_key_first(array_slice($array, -1));    }}?>