Php create array null

Php create array null

// Before php 5.4
$array = array(1,2,3);

// since php 5.4 , short syntax
$array = [1,2,3];

// I recommend using the short syntax if you have php version >= 5.4

Used to creating arrays like this in Perl?

Looks like we need the range() function in PHP:

$array = array_merge (array( ‘All’ ), range ( ‘A’ , ‘Z’ ));
?>

You don’t need to array_merge if it’s just one range:

There is another kind of array (php>= 5.3.0) produced by

$array = new SplFixedArray(5);

Standard arrays, as documented here, are marvellously flexible and, due to the underlying hashtable, extremely fast for certain kinds of lookup operation.

Supposing a large string-keyed array

$arr=[‘string1’=>$data1, ‘string2’=>$data2 etc. ]

when getting the keyed data with

php does *not* have to search through the array comparing each key string to the given key (‘string1’) one by one, which could take a long time with a large array. Instead the hashtable means that php takes the given key string and computes from it the memory location of the keyed data, and then instantly retrieves the data. Marvellous! And so quick. And no need to know anything about hashtables as it’s all hidden away.

However, there is a lot of overhead in that. It uses lots of memory, as hashtables tend to (also nearly doubling on a 64bit server), and should be significantly slower for integer keyed arrays than old-fashioned (non-hashtable) integer-keyed arrays. For that see more on SplFixedArray :

Unlike a standard php (hashtabled) array, if you lookup by integer then the integer itself denotes the memory location of the data, no hashtable computation on the integer key needed. This is much quicker. It’s also quicker to build the array compared to the complex operations needed for hashtables. And it uses a lot less memory as there is no hashtable data structure. This is really an optimisation decision, but in some cases of large integer keyed arrays it may significantly reduce server memory and increase performance (including the avoiding of expensive memory deallocation of hashtable arrays at the exiting of the script).

When creating arrays , if we have an element with the same value as another element from the same array, we would expect PHP instead of creating new zval container to increase the refcount and point the duplicate symbol to the same zval. This is true except for value type integer.
Example:

$arr = [‘bebe’ => ‘Bob’, ‘age’ => 23, ‘too’ => 23 ];
xdebug_debug_zval( ‘arr’ );

(refcount=2, is_ref=0)
array (size=3)
‘bebe’ => (refcount=1, is_ref=0)string ‘Bob’ (length=3)
‘age’ => (refcount=0, is_ref=0)int 23
‘too’ => (refcount=0, is_ref=0)int 23

but :
$arr = [‘bebe’ => ‘Bob’, ‘age’ => 23, ‘too’ => ’23’ ];
xdebug_debug_zval( ‘arr’ );

(refcount=2, is_ref=0)
array (size=3)
‘bebe’ => (refcount=1, is_ref=0)string ‘Bob’ (length=3)
‘age’ => (refcount=0, is_ref=0)int 23
‘too’ => (refcount=1, is_ref=0)string ’23’ (length=2)
or :

$arr = [‘bebe’ => ‘Bob’, ‘age’ => [1,2], ‘too’ => [1,2] ];
xdebug_debug_zval( ‘arr’ );

(refcount=2, is_ref=0)
array (size=3)
‘bebe’ => (refcount=1, is_ref=0)string ‘Bob’ (length=3)
‘age’ => (refcount=2, is_ref=0)
array (size=2)
0 => (refcount=0, is_ref=0)int 1
1 => (refcount=0, is_ref=0)int 2
‘too’ => (refcount=2, is_ref=0)
array (size=2)
0 => (refcount=0, is_ref=0)int 1
1 => (refcount=0, is_ref=0)int 2

This function makes (assoc.) array creation much easier:

function arr (. $array )< return $array ; >
?>

It allows for short syntax like:

$arr = arr ( x : 1 , y : 2 , z : 3 );
?>

Instead of:

$arr = [ «x» => 1 , «y» => 2 , «z» => 3 ];
// or
$arr2 = array( «x» => 1 , «y» => 2 , «z» => 3 );
?>

Sadly PHP 8.2 doesn’t support this named arguments in the «array» function/language construct.

Источник

How to Create an Empty Array in php

In php, there are three ways you can create an empty array. Creating an empty array can be useful if your data is dynamic.

$emptyArray = []; $emptyArray = array(); $emptyArray = (array) null

When working with arrays and collections of data in php, it is useful to be able to create and use different data structures easily.

We can easily create an empty array in php.

There are three ways you can use to define an empty array in php.

The first is similar to defining an array in JavaScript, where an empty array is defined with two open square brackets.

The second way to define an empty array in php is with the array() function.

The third and final way to create an empty array in php is by casting “null” to type array.

In our opinion, the easiest way to initialize an empty array with no elements is the first way.

How to Add Elements to an Empty Array in php

After initializing an empty array, adding elements is easy. We can add items to an array with the php array_push() function.

Below is a simple example in php of creating an empty array and adding three elements to the array.

$emptyArray = []; print_r($emptyArray); array_push($emptyArray,"bear","snake","horse"); print_r($emptyArray); //Output: Array ( ) Array ( [0] => bear [1] => snake [2] => horse )

Hopefully this article has been useful for you to learn how to create an empty array in your php programs.

Other Articles You’ll Also Like:

• 1. preg_replace php – Use Regex to Search and Replace
• 2. php cosh – Find Hyperbolic Cosine of Number Using php cosh() Function
• 3. php getimagesize – Get Height, Width and Image File Type
• 4. Get Query String from URL in php
• 5. How to Check If String Contains Substring in PHP
• 6. php array_filter() – Filter Array Elements with Function in php
• 7. php Trig – Using Trigonometric Functions in php for Trigonometry
• 8. php Square Root with sqrt Function
• 9. php array_diff() – Find Elements of Array Not Present in Other Arrays
• 10. How to Get Current System IP Address in php

About The Programming Expert

The Programming Expert is a compilation of a programmer’s findings in the world of software development, website creation, and automation of processes.

Programming allows us to create amazing applications which make our work more efficient, repeatable and accurate.

At the end of the day, we want to be able to just push a button and let the code do it’s magic.

You can read more about us on our about page.

Источник

Объявить пустой массив php?

Как объявить пустой массив?
если $arr = array();
то заполнение начнется с индекса 1($arr[1]).
Можно так:
$arr = array();
unset($arr[0]);
но как это сделать правильнее и проще?

Оценить 2 комментария

$arr = array(); array_push($arr, "test"); print_r($arr);

 'January', 'February', 'March'); print_r($firstquarter); ?>

Как вариант, можете после наполнения массива, вставить в начало элемент, и убрать. Что двинет все ключи на 1.

$array = [1,2,3]; array_unshift($array, '' ); unset($array[0]);

Нужно пустой массив объявить. Чтобы там не было элементов. Объявить, но так, чтоб он был не инициализирован.

Алексей Объявляйте массив как обычно (array() или []). При добавлении в массив указываете нужный ключ ($arr[1] = 3.14)

krypt3r: а если у меня заполнение идёт через array_push? Тогда у меня первый элемент будет пустой, на сайте это лишняя строчка пустая.

Алексей: Будьте добры, приведите полностью код который эквивалентен второму листингу. Я думаю вы не имеете ввиду

$arr = array(); unset($arr[0]); array_push($arr, 1);

Алексей: вы каким то не тем php пользуетесь — при инициализации массива в него никакие элементы не добавляются и если выполнить array_push() после инициализации, то в массиве появится элемент с индексом 0.

Источник