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Introduction notes to PHP zero Foundation (13): array related functions

2022-04-23 16:14:00 【Peng Shiyu psy】

Array related functions

Custom array print function , Easy to view

function print_array($array){
    foreach($array as $key => $value){
        echo "$key => $value\n";
    }
}


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Sorting function

according to ASCII Sort code

sort Yes array By itself （value） Ascending sort .( Subscript rearrangement )

sort(array &$array, int $flags = SORT_REGULAR): bool


// eg:
$arr = ['Tom', 'Jack', 'Steve'];

sort($arr);

print_array($arr);
// 0 => Jack
// 1 => Steve
// 2 => Tom


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rsort Yes array By itself （value） null .

rsort(array &$array, int $flags = SORT_REGULAR): bool


// eg:
$arr = ['Tom', 'Jack', 'Steve'];

rsort($arr);

print_array($arr);
// 0 => Tom
// 1 => Steve
// 2 => Jack

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asort Yes array Sort itself in ascending order ( Subscript reserved )

asort(array &$array, int $flags = SORT_REGULAR): bool


// eg:
$arr = ['Tom', 'Jack', 'Steve'];

asort($arr);

print_array($arr);
// 1 => Jack
// 2 => Steve
// 0 => Tom

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arsort Yes array Sort itself in descending order

arsort(array &$array, int $flags = SORT_REGULAR): bool


// eg:
$arr = ['Tom', 'Jack', 'Steve'];

arsort($arr);

print_array($arr);
// 0 => Tom
// 2 => Steve
// 1 => Jack

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ksort Yes array Press the button itself （key） Ascending sort .

ksort(array &$array, int $flags = SORT_REGULAR): bool


// eg:
$arr = ['Tom', 'Jack', 'Steve'];

ksort($arr);

print_array($arr);
// 0 => Tom
// 1 => Jack
// 2 => Steve

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krsort Yes array Press the key itself （key） null .

krsort(array &$array, int $flags = SORT_REGULAR): bool


// eg:
$arr = ['Tom', 'Jack', 'Steve'];

krsort($arr);

print_array($arr);
// 2 => Steve
// 1 => Jack
// 0 => Tom

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shuffle Random disruption

shuffle(array &$array): bool


// eg:
$arr = ['Tom', 'Jack', 'Steve'];

shuffle($arr);

print_array($arr);
// 0 => Jack
// 1 => Steve
// 2 => Tom

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Pointer function

reset take array The internal pointer of the array returns to the first cell and returns the value of the first array cell .

end take array The internal pointer to the last cell and returns its value .

next Move the internal pointer in the array one bit forward

prev Returns the internal pointer of an array to one bit

current Returns the current value in the array

key Returns the key name of the current cell in the array .

Be careful ：next and prev Move the pointer , May move out of the array , Only through end perhaps reset Reset pointer

Example

Other functions

count Statistical array 、Countable The number of all elements in the object

count(Countable|array $value, int $mode = COUNT_NORMAL): int

// eg:
$arr = [1, 2, 3, 4, 5];

echo count($arr);
// 5

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array_push take array As a stack , And push the incoming variable into array At the end of .

array_push(array &$array, mixed $value1, mixed $... = ?): int

//  The same effect as the following ：
$array[] = $var;

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array_pop Pop up and return array The value of the last element

array_shift take array The first cell of is moved out and returned as a result

array_unshift Insert one or more cells at the beginning of an array

data structure

Stack Pressing stack ,FILO First in, then out
queue line up ,FIFO fifo

Implementation stack ：

front array_unshift/array_shift
Back array_push/array_pop

<?php $arr = []; //  Push  array_push($arr, 1); array_push($arr, 2); array_push($arr, 3); //  Out of the stack  echo array_pop($arr), array_pop($arr), array_pop($arr); // 321 













Implementation queue ：

Last in first out array_push/array_shift
Forward and out array_unshift/array_pop

<?php $arr = []; //  The team  array_push($arr, 1); array_push($arr, 2); array_push($arr, 3); //  Out of the team  echo array_shift($arr), array_shift($arr), array_shift($arr); // 123 













array_reverse Returns a new array whose cells are in reverse order

array_reverse(array $array, bool $preserve_keys = false): array

// eg
$arr = [1, 2, 3, 4, 5];

print_array(array_reverse($arr));
// 0 => 5
// 1 => 4
// 2 => 3
// 3 => 2
// 4 => 1

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in_array Check if there is a value in the array

in_array(mixed $needle, array $haystack, bool $strict = false): bool

// eg
$arr = [1, 2, 3, 4, 5];

var_dump(in_array(5, $arr));
// bool(true)


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array_keys Returns some or all key names in the array

array_keys(array $array): array

array_keys(array $array, mixed $search_value, bool $strict = false): array


// eg
$arr = ['Tom', 'Jack', 'Steve'];

echo json_encode(array_keys($arr));
// [0,1,2]

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array_values return input All values in the array and numerically index them .

array_values(array $array): array

// eg
$arr = ['Tom', 'Jack', 'Steve'];

echo json_encode(array_values($arr));
// ["Tom","Jack","Steve"]

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