Populate array with values formed by concatenating a range of numbers to a static string-CodePudding

I want to create a function that generates an array of elements which consist of incremented numbers appended to a static string/prefix and looks like this:

$arr = [
    'file1',
    'file2',
    'file3',
    'file4',
    'file5',
];

I know I can create a simple loop like this one:

$arr = [];
for( $i = 1; $i <= 5; $i    ){
    $arr[] = 'file' . $i;
}

But the idea is to give the parameters $text = file, $start = 1, $elements = 5 and optional $step = 1 and use built-in php functions to achieve it.

I tried something like:

$arr = array_merge( array_fill( 0, 5, 'file' ), range( 1, 5, 1 ) );

But from that one I got

$arr = [
    "file",
    "file",
    "file",
    "file",
    "file",
    0,
    1,
    2,
    3,
    4,
    5,
];

CodePudding user response：

You can choose a functional style or classic loop approach using your parameters. I am using the same equation in map() and whileloop() to determine the end of the range and avoid the use of an additional counter variable. The forloop() function is a little easier to understand, but has to maintain an extra variable which must be incremented to get the number of elements right. (Demo)

function map($text = 'file', $elements = 5, $start = 1, $step = 1) {
    $end = $start   $elements * $step - 1;
    return array_map(
        fn($i) => $text . $i,
        range($start, $end, $step)
    );
}

function whileloop($text = 'file', $elements = 5, $start = 1, $step = 1) {
    $result = [];
    $end = $start   $elements * $step - 1;
    while ($start <= $end) {
        $result[] = $text . $start;
        $start  = $step;
    }
    return $result;
}

function forloop($text = 'file', $elements = 5, $start = 1, $step = 1) {
    $result = [];
    for ($i = 0; $i < $elements;   $i, $start  = $step) {
        $result[] = $text . $start;
    }
    return $result;
}

CodePudding user response：

You are almost there. You can generate the array via range and then prepend file via array_map like below:

<?php

$arr = array_map(fn($e) => 'file'. $e,range(1,5));

print_r($arr);

CodePudding user response：

If you want to keep your beginner-friendly and readable syntax, you can simply modify your code like such:

$arr = [];
for( $i = $start; $i < $start   ($elements * $step); $i  = $step ){
    $arr[] = $text . $i;
}

Edit: be careful if your variables come from user input: a negative $step could result in an infinite loop.

CodePudding user response：

If you want to give those parameters, then I believe you are looking at writing a function. In the function a for loop should achieve what you want.

function heaven_knows_why($text, $start, $elements, $step = 1)
{
    $arr = [];
    for( $i = $start, $j=1, $s=$start; $j <= $elements; $j  , $i  , $s  = $step ){
        $arr[] = $text . $s;
    }
    return $arr;
}

print_r(heaven_knows_why('duh', 1, 5));
print_r(heaven_knows_why('duh', 1, 5, 2));

RESULTS

Array
(
    [0] => duh1
    [1] => duh2
    [2] => duh3
    [3] => duh4
    [4] => duh5
)
Array
(
    [0] => duh1
    [1] => duh3
    [2] => duh5
    [3] => duh7
    [4] => duh9
)

A Demo