php create array assignment

5 Ways to Create an Array in PHP

Last updated: January 10, 2024

PHP, as a versatile server-side scripting language, offers various ways to create and manipulate arrays. An array is a structured data type that can hold multiple values at once, and creating arrays efficiently is crucial for writing clean and effective code. In PHP, arrays can be indexed by numbers, called indexed arrays, or by strings, known as associative arrays. Below, we explore several methods for array creation in PHP, covering traditional and newer techniques suitable for a variety of use cases.

Using array() function, short array syntax, range function, using array_fill(), using compact function.

The array() function is one of the most common ways to create an array in PHP. It’s a straightforward and readable approach to initializing either an indexed or an associative array.

Decide whether you need an indexed or an associative array.
Use the array() function to define the elements of the array.
Assign the result to a variable.

Performance: The array() function is a basic internal PHP function with no significant performance implications for small to medium-sized arrays.

Pros: The array() function syntax is clear and widely understood, making the code easy to read. Also, it is compatible with all versions of PHP.

Cons: This method can be a bit verbose, especially with the newer square bracket syntax available.

Since PHP 5.4, a new short array syntax has been introduced, which uses square brackets [] instead of the array() function. This is similar to arrays in JavaScript and other programming languages, and tends to be less verbose.

Identify the array elements you want to initialize.
Use the square bracket syntax to define the array.
Assign the contents within the square brackets to a variable.

Performance: The performance of the short array syntax is on par with the traditional array() function. However, reduced code clutter might lead to slightly faster coding and debugging times.

Advantages: More concise code, modern look, and ease of typing compared to the traditional array() function.

Limitations: It is not supported in PHP versions prior to 5.4, which could be a drawback when working on older code bases.

The range() function provides an easy way to quickly initialize an array with a sequence of numbers or letters. This is particularly useful when you need a range of values without manually typing each one.

Define the start and end of the sequence.
Optionally define the step between values in the sequence.
Use the range() function to create the array.

Performance Discussion: The range() function is implemented in C within the PHP core, making it a fast and efficient way to generate large sequences of numbers or characters.

Advantages: Very concise for creating simple sequences without needing explicit loops or manual enumeration.

Limitations: As a specialized function, it is limited to generating sequences and cannot be used for arbitrary array data.

The array_fill() function creates an array filled with a specified value. This is an optimal solution when you need to initialize an array with the same value across all elements.

Specify the starting index.
Specify the number of elements you want the array to contain.
Decide on the value with which you want to fill the array.
Use the array_fill() function to create an array.

Performance Discussion: The array_fill() function has good performance for setting up equally valued elements, especially on large arrays, and is implemented efficiently in PHP.

Advantages: Especially useful for initializing large arrays with default values and simplifying the code.

Limitations: Limited to only one value, and it can be inefficient for associative arrays or small arrays where manual assignment makes more sense.

The compact() function creates an associative array from existing variables. This is an elegant way to create an associative array using shorthand syntax and already defined variables, rather than manually entering key-value pairs.

Define the individual variables with their respective values.
Pass variable names as arguments to the compact() function.
Use the function result as the newly created associative array.

Performance Discussion: The compact() function has no significant performance overhead and can make for very readable and maintainable code, especially with many variables.

Pros: Makes the code cleaner and avoids repetitive manual array assignment.

Limitations: It assumes that variable names are meaningful as keys, which is not always the case. Variable names used as keys also mean you must maintain naming consistency in your code.

In summary, PHP provides multiple avenues for array creation, each with its context where it shines. Whether you are creating indexed or associative arrays, working with sequences, or needing to initialize arrays of a certain size, choosing the right method depends on your specific use case and constraints such as PHP version compatibility. Simple arrays are often most easily and legibly created with the short array syntax or the traditional array() function. For specific sequences or patterns of values, functions like range() and array_fill() provide efficient shortcuts. When dealing with a collection of variables, compact() may be your best friend. Ultimately, understanding the options allows for more readable, maintainable, and effective PHP programming.

Next Article: Exploring Indexed and Associative Arrays in PHP

Series: PHP Data Structure Tutorials

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Function Reference
Variable and Type Related Extensions
Introduction
Predefined Constants
Sorting Arrays
array — Create an array
array_all — Checks if all array elements satisfy a callback function
array_any — Checks if at least one array element satisfies a callback function
array_change_key_case — Changes the case of all keys in an array
array_chunk — Split an array into chunks
array_column — Return the values from a single column in the input array
array_combine — Creates an array by using one array for keys and another for its values
array_count_values — Counts the occurrences of each distinct value in an array
array_diff — Computes the difference of arrays
array_diff_assoc — Computes the difference of arrays with additional index check
array_diff_key — Computes the difference of arrays using keys for comparison
array_diff_uassoc — Computes the difference of arrays with additional index check which is performed by a user supplied callback function
array_diff_ukey — Computes the difference of arrays using a callback function on the keys for comparison
array_fill — Fill an array with values
array_fill_keys — Fill an array with values, specifying keys
array_filter — Filters elements of an array using a callback function
array_find — Returns the first element satisfying a callback function
array_find_key — Returns the key of the first element satisfying a callback function
array_flip — Exchanges all keys with their associated values in an array
array_intersect — Computes the intersection of arrays
array_intersect_assoc — Computes the intersection of arrays with additional index check
array_intersect_key — Computes the intersection of arrays using keys for comparison
array_intersect_uassoc — Computes the intersection of arrays with additional index check, compares indexes by a callback function
array_intersect_ukey — Computes the intersection of arrays using a callback function on the keys for comparison
array_is_list — Checks whether a given array is a list
array_key_exists — Checks if the given key or index exists in the array
array_key_first — Gets the first key of an array
array_key_last — Gets the last key of an array
array_keys — Return all the keys or a subset of the keys of an array
array_map — Applies the callback to the elements of the given arrays
array_merge — Merge one or more arrays
array_merge_recursive — Merge one or more arrays recursively
array_multisort — Sort multiple or multi-dimensional arrays
array_pad — Pad array to the specified length with a value
array_pop — Pop the element off the end of array
array_product — Calculate the product of values in an array
array_push — Push one or more elements onto the end of array
array_rand — Pick one or more random keys out of an array
array_reduce — Iteratively reduce the array to a single value using a callback function
array_replace — Replaces elements from passed arrays into the first array
array_replace_recursive — Replaces elements from passed arrays into the first array recursively
array_reverse — Return an array with elements in reverse order
array_search — Searches the array for a given value and returns the first corresponding key if successful
array_shift — Shift an element off the beginning of array
array_slice — Extract a slice of the array
array_splice — Remove a portion of the array and replace it with something else
array_sum — Calculate the sum of values in an array
array_udiff — Computes the difference of arrays by using a callback function for data comparison
array_udiff_assoc — Computes the difference of arrays with additional index check, compares data by a callback function
array_udiff_uassoc — Computes the difference of arrays with additional index check, compares data and indexes by a callback function
array_uintersect — Computes the intersection of arrays, compares data by a callback function
array_uintersect_assoc — Computes the intersection of arrays with additional index check, compares data by a callback function
array_uintersect_uassoc — Computes the intersection of arrays with additional index check, compares data and indexes by separate callback functions
array_unique — Removes duplicate values from an array
array_unshift — Prepend one or more elements to the beginning of an array
array_values — Return all the values of an array
array_walk — Apply a user supplied function to every member of an array
array_walk_recursive — Apply a user function recursively to every member of an array
arsort — Sort an array in descending order and maintain index association
asort — Sort an array in ascending order and maintain index association
compact — Create array containing variables and their values
count — Counts all elements in an array or in a Countable object
current — Return the current element in an array
each — Return the current key and value pair from an array and advance the array cursor
end — Set the internal pointer of an array to its last element
extract — Import variables into the current symbol table from an array
in_array — Checks if a value exists in an array
key — Fetch a key from an array
key_exists — Alias of array_key_exists
krsort — Sort an array by key in descending order
ksort — Sort an array by key in ascending order
list — Assign variables as if they were an array
natcasesort — Sort an array using a case insensitive "natural order" algorithm
natsort — Sort an array using a "natural order" algorithm
next — Advance the internal pointer of an array
pos — Alias of current
prev — Rewind the internal array pointer
range — Create an array containing a range of elements
reset — Set the internal pointer of an array to its first element
rsort — Sort an array in descending order
shuffle — Shuffle an array
sizeof — Alias of count
sort — Sort an array in ascending order
uasort — Sort an array with a user-defined comparison function and maintain index association
uksort — Sort an array by keys using a user-defined comparison function
usort — Sort an array by values using a user-defined comparison function