Split String Into Array and Append Prev Value

Question

I have this string:

var/log/file.log

I eventually want to end up with an array looking like this:

Array => [
    '1' => 'var',
    '2' => 'var/log',
    '3' => 'var/log/file.log'
]

I currently have this:

<?php
    $string = 'var/log/file.log';
    $array = explode('/', $string);
    $output = [
        1 => $array[0],
        2 => $array[0]. '/' .$array[1],
        3 => $array[0]. '/' .$array[1]. '/' .$array[2]
    ];

    echo '<pre>'. print_r($output, 1) .'</pre>';

This feels really counter-intuitive and I'm not sure if there's already something built into PHP that can take care of this.

How do I build an array using appending previous value?

Answer 1

<?php
$string = 'var/log/some/other/directory/file.log';
$array = explode('/', $string);

$i = 0;
foreach ($array as $data) {
    $output[] = isset($output) ? $output[$i - 1] . '/' . $data : $data;
    $i++;
}


echo '<pre>';

print_r($output);

A simpler solution is above. You simple set your new array field to be a concatenation of your previous one from your new array and the current one from your foreach.

Output is:

Array
(
    [0] => var
    [1] => var/log
    [2] => var/log/some
    [3] => var/log/some/other
    [4] => var/log/some/other/directory
    [5] => var/log/some/other/directory/file.log
)

Answer 2

This solution takes the approach of starting with your input path, and then removing a path one by one, adding the remaining input to an array at each step. Then, we reverse the array as a final step to generate the output you want.

$input = "var/log/file.log";
$array = [];
while (preg_match("/\//i", $input)) {
    array_push($array, $input);
    $input = preg_replace("/\/[^\/]+$/", "", $input);
    echo $input;
}
array_push($array, $input);
$array = array_reverse($array);
print_r($array);

Array
(
    [0] => var
    [1] => var/log
    [2] => var/log/file.log
)

The above call to preg_replace strips off the final path of the input string, including the forward slash. This is repeated until there is only one final path component left. Then, we add that last component to the same array.

Answer 3

You could do something like this with a foreach

<?php
$string = 'var/log/file.log';
$array = explode('/', $string);

$last = '';
$output = array();
foreach ($array as $key => $value) {
    $result = $last.$value;
    $output[$key] = $result;
    $last = $result.'/';
}

echo '<pre>'. print_r($output, 1) .'</pre>';

Answer 4

You can get parent directory in a loop and add it to output variable. For example with help the following algorithm:

$path = 'var/log/file.log';
$output = [];

$pos = strlen($path);
while ($pos !== false) {
    $path = substr($path, 0, $pos);
    array_unshift($output, $path);
    $pos = strrpos($path, DIRECTORY_SEPARATOR);
}

or with dirname() function

$path = 'var/log/file.log';
$output = [];

do {
  array_unshift($output, $path);
  $path = dirname($path);
} while ($path !== '.');

Also, you can work with $path string as an array of chars and find directory separator in it:

$path = 'var/log/file.log';
$output = [];

$tmp = '';
$len = strrpos($path, DIRECTORY_SEPARATOR); // you can use strlen instead of strrpos,
                                            // but it'll look over filename also
for ($i = 0; $i < $len; $i++) {        
    if ($path[$i] === DIRECTORY_SEPARATOR) {
        $output[] = $tmp;
    }
    $tmp .= $path[$i];
}
$output[] = $path;

but keep in mind you couldn't use this way if $path string has multibyte encoding

The result of all methods will be:

Array (
     [0] => var
     [1] => var/log
     [2] => var/log/file.log 
)

Answer 5

Because I can't help myself, I benchmarked all these answers. @Yoshi's (deleted, but you can see the code below) answer came a fairly clear first, followed by @OliverNybo (about 15% slower), @pr1nc3 (about 35% slower), a gap to mine and @MaximFedorov's first and second answer (about 55-75% slower), then another gap to @TimBiegeleisen and finally to @MaximFedorov's last answer (which didn't actually return the correct result). Here are the results for 100,000 iterations (times in seconds):

Here's the testing code. Note I've removed a call to array_reverse where it was used as it doesn't do anything other than change the order of output.

<!DOCTYPE html>
<html>
<head>
    <style type="text/css">
        table {
            border-collapse: collapse;align-content:
        }
        td, th {
            border: 1px solid black;
            padding: 5px;
        }
    </style>
</head>
<body>
<pre>
<?php
$string = 'var/log/some/other/directory/file.log';
$elapsed = array();
foreach (array('TimBiegeleisen', 'pr1nc3', 'OliverNybo', 'MaximFedorov1', 'MaximFedorov2', 'MaximFedorov3', 'Nick') as $func) {
    $start = explode(' ', microtime());
    for ($i = 0; $i < 100000; $i++) $func($string);
    $elapsed[$func] = elapsed_time($start);
}
asort($elapsed);
$fastest = min($elapsed);

echo "<table><tr><th>Function</th><th>Elapsed Time</th><th>Delta</tr>";
foreach ($elapsed as $key => $value) {
    echo "<td>$key</td><td>$value</td>";
    echo "<td>" . sprintf("%.0f%%", ($value - $fastest) / $fastest * 100) . "</td></tr>";
}
echo "</table>\n";

function TimBiegeleisen($input) {
    $array = [];
    while (preg_match("/\//i", $input)) {
        array_push($array, $input);
        $input = preg_replace("/\/[^\/]+$/", "", $input);
    }
    array_push($array, $input);
    return $array;
//  return array_reverse($array);   
}

function pr1nc3($string) {
    $array = explode('/', $string);

    $i = 0;
    foreach ($array as $data) {
        $output[] = isset($output) ? $output[$i - 1] . '/' . $data : $data;
        $i++;
    }
    return $output;
}

function OliverNybo($string) {
    $array = explode('/', $string);

    $last = '';
    $output = array();
    foreach ($array as $key => $value) {
        $result = $last.$value;
        $output[$key] = $result;
        $last = $result.'/';
    }   
    return $output;
}

function MaximFedorov1($path) {
    $output = [];

    $pos = strlen($path);
    while ($pos !== false) {
        $path = substr($path, 0, $pos);
        array_unshift($output, $path);
        $pos = strrpos($path, '/');
    }
    return $output;
}

function MaximFedorov2($path) {
    $output = [];

    do {
      array_unshift($output, $path);
      $path = dirname($path);
    } while ($path !== '.');
    return $output;
}

function MaximFedorov3($path) {
    $output = [];
    $tmp = '';
    $len = strrpos($path, '/'); // you can use strlen instead of strrpos,
                                                // but it'll look over filename also
    for ($i = 0; $i < $len; $i++) {        
        if ($path[$i] === '/') {
            $output[] = $tmp;
        }
        $tmp .= $path[$i];
    }
    $output[] = $path;
    return $output;
}

function Nick($string) {
    $array = explode('/', $string);
    for ($c = count($array); $c > 0; ) {
        $output[--$c] = implode('/', $array);
        array_pop($array);
    }
    return $output;
//  return array_reverse($output)
}

function Yoshi($input) {
    $output = explode('/', $input);

    for ($i = 1, $lim = \count($output); $i < $lim; $i++) {
        $output[$i] = $output[$i - 1] . '/' . $output[$i];
    }
    return $output;
}

function elapsed_time(array $start) {
    $now = explode(' ', microtime());
    $deltasec = $now[1] - $start[1];
    $deltamsec = (float)$now[0] - (float)$start[0];
    return $deltasec + $deltamsec;
}


?>
</pre>
</body>
</html>

Answer 6

There are a lot of good answers here already but here's another slightly different way of doing this:

$string = 'var/log/some/other/directory/file.log';
$array = explode('/', $string);
for ($c = count($array); $c > 0; ) {
    $output[--$c] = implode('/', $array);
    array_pop($array);
}
for ($i = 0; $i < count($output); $i++) {
    echo "$output[$i]\n";
}

Output:

var 
var/log 
var/log/some 
var/log/some/other 
var/log/some/other/directory 
var/log/some/other/directory/file.log

Demo on 3v4l.org