Php array set length

Php array set length

// 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.

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How to Set the Size of an Array in PHP: A Complete Guide

Learn how to set the size of an array in PHP with this complete guide. Explore different methods, including using SplFixedArray and initializing an array with a predetermined size.

• Using SplFixedArray
• Initializing an Array with a Predetermined Size
• Getting the Size of an Array
• Padding an Array to a Specified Length
• Changing the Size of an Array
• Other simple code examples for setting array size in PHP
• Conclusion
• How to set the size of an array in PHP?
• How do you declare an array size 10?
• How do I declare an array of size 50?
• How to create array of size n in PHP?

Arrays in PHP are dynamic and do not have a set size, but there are ways to specify a fixed size. This post will explore different ways to set the size or length of an array in PHP. If you are looking for a complete guide to setting the size of an array in PHP, then you have come to the right place. Whether you are a beginner or an experienced PHP developer, this guide will provide you with everything you need to know.

Using SplFixedArray

SplFixedArray is a class in the Standard PHP Library that allows for fixed-size arrays . It is designed to provide better performance compared to regular arrays because the memory allocation is done at the time of creation. The array size cannot be changed after it has been created.

Here is an example code to create a fixed-size array with 5 elements:

$fixedArray = new SplFixedArray(5); 

The above code creates a fixed array with 5 elements. You can add or remove elements in a fixed array using the same methods as a regular array. However, you cannot exceed the maximum size of the array, which is set at the time of creation.

The advantage of using SplFixedArray is that it provides better performance compared to regular arrays, especially when dealing with large amounts of data. However, it is not suitable for all scenarios because the array size cannot be changed after creation .

Initializing an Array with a Predetermined Size

Another way to set the size of an array in PHP is to initialize an array with a predetermined size. You can use the array_fill() function to create an array with a fixed size.

Here is an example code to create an array with 5 null elements:

$array = array_fill(0, 5, null); 

The above code creates an array with 5 null elements. You can add or remove elements in a predetermined size array using the same methods as a regular array. However, you cannot exceed the maximum size of the array, which is set at the time of creation.

The advantage of using this method is that it is simple and easy to use. However, it may not provide the best performance compared to SplFixedArray or regular arrays.

Getting the Size of an Array

To get the number of elements in an array, you can use the count() or sizeof() function. Both functions return the same value, which is the number of elements in the array.

Here is an example code to get the number of elements in an array:

$array = array(1, 2, 3, 4, 5); echo count($array); // returns 5 

You can use either count() or sizeof() to get the size of an array. However, sizeof() is an alias of count() and is provided for backward compatibility.

It is important to note that the length property in JavaScript is different from count() or sizeof() in PHP. The length property in JavaScript returns the highest index number plus one, while count() or sizeof() in PHP returns the number of elements in the array.

Padding an Array to a Specified Length

To pad an array with a value to a specified length, you can use the array_pad() function. This function adds elements to the beginning or end of an array to make it the specified length.

Here is an example code to pad an array with 0’s to a length of 5:

$array = array(1, 2, 3); $paddedArray = array_pad($array, 5, 0); 

The above code pads the array with 0’s to a length of 5. You can remove padding from an array using the array_slice() function.

The advantage of using array_pad() is that it allows you to easily pad an array to a specified length. However, it may not be suitable for all scenarios because it modifies the original array.

Changing the Size of an Array

To change the size of a fixed array to a new size, you can use the SplFixedArray::setSize() method. This method changes the size of the fixed array to a new size. You can also add or remove elements when changing the size of an array.

Here is an example code to change the size of a fixed array to 10:

$fixedArray = new SplFixedArray(5); $fixedArray->setSize(10); 

The above code changes the size of the fixed array to 10. You can add or remove elements in a fixed array using the same methods as a regular array. However, you cannot exceed the maximum size of the array, which is set at the time of creation.

The advantage of changing the size of an array is that it allows you to dynamically adjust the size of the array based on your needs. However, it may not provide the best performance compared to fixed-size arrays.

Other simple code examples for setting array size in PHP

In Php , for example, php array size code example

echo count($my_array); echo sizeof($my_array); // alias

Conclusion

In conclusion, there are different ways to set the size or length of an array in PHP, including using SplFixedArray or initializing an array with a predetermined size. The count() or sizeof() function can be used to get the number of elements in an array. The array_pad() function can be used to pad an array to a specified length. Changing the size of an array can be done using SplFixedArray::setSize() or by adding or removing elements. Each method has its advantages and disadvantages and should be used based on the specific needs of the project.

I hope this guide has provided you with everything you need to know about setting the size of an array in PHP. Whether you are a beginner or an experienced PHP developer, this guide will help you to work with arrays more effectively. If you have any questions or comments, please feel free to leave them below.

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