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Searching and Counting

array_key_exists($m,$arr) returns true if the key $m can be found in $arr. in_array ($m, $arr[,$b=false])  returns true if the value $m can be found in $arr. If $b is true, the types are also compared. array_search($m,$arr[,$b=false]) returns the first matching key of the value $m. FALSE is returned if the value does not exist. If $b is true, the types are also compared. count($arr[,$i]) or sizeof($arr[,$i]) returns the number of elements in $arr. If $i is set to COUNT_RECURSIVE, the elements in sub arrays will be counted as well. array_count_values($arr) returns an array which uses the values of $arr as keys, and their frequencies as values. 

<!DOCTYPE html><html><head></head>
<body>
<?php
$a=["hello",1,1,"hello",1,2];
print_r(array_count_values($a));
?> 
</body></html>

Array ( [hello] => 2 [1] => 3 [2] => 1 )
PHP 7.3 added array_key_first($arr) and array_key_last($arr), which return the first and last keys of an array without needing to reset the internal pointer or call end()/key(). is_countable($m), also from PHP 7.3, returns true if $m is an array or an object implementing Countable. It is useful for guarding a count() call, since passing something uncountable to count() is a TypeError as of PHP 8.

PHP 8.1’s array_is_list($arr) returns true if $arr’s keys are the integers 0, 1, 2, and so on with no gaps. In other words, it checks whether $arr is a plain ‘list’ rather than an associative array. 

<!DOCTYPE html><html><head></head>
<body>
<?php
$fruit = ["a" => "apple", "b" => "banana", "c" => "cherry"];
echo array_key_first($fruit) . "<br />";
echo array_key_last($fruit) . "<br />";

var_dump(is_countable($fruit));
var_dump(is_countable("not an array"));

$list = ["x", "y", "z"];
$assoc = ["a" => "x", "b" => "y"];
$gappy = [1 => "x", 2 => "y"];

var_dump(array_is_list($list));
var_dump(array_is_list($assoc));
var_dump(array_is_list($gappy));
?>
</body></html>

a
c
bool(true) bool(false) bool(true) bool(false) bool(false)