PHP | Remove element from array with reordering?

问题:

How can I remove an element of an array, and reorder afterwards, without having an empty element in the array?

<?php
   $c = array( 0=>12,1=>32 );
   unset($c[0]); // will distort the array.
?>

Answer / Solution: array array_values ( array $input ).

<?php
   $c = array( 0=>12,1=>32 );
   unset($c[0]);
   print_r(array_values($c));
   // will print: the array cleared
?>

回答1:

array_values($c)

will return a new array with just the values, indexed linearly.

回答2:

If you are always removing the first element, then use array_shift() instead of unset().

Otherwise, you should be able to use something like $a = array_values($a).

回答3:

Another option would be array_splice(). This reorders numeric keys and appears to be a faster method if you are crunching enough data to care. But I like unset() array_values() for readability.

array_splice( $array, $index, $num_elements_to_remove);

http://php.net/manual/en/function.array-splice.php

Speed test:

    ArraySplice process used 7468 ms for its computations
    ArraySplice spent 918 ms in system calls
    UnsetReorder process used 9963 ms for its computations
    UnsetReorder spent 31 ms in system calls

Test Code:

function rutime($ru, $rus, $index) {
    return ($ru["ru_$index.tv_sec"]*1000 + intval($ru["ru_$index.tv_usec"]/1000))
     -  ($rus["ru_$index.tv_sec"]*1000 + intval($rus["ru_$index.tv_usec"]/1000));
}

function time_output($title, $rustart, $ru) {
        echo $title . " process used " . rutime($ru, $rustart, "utime") .
            " ms for its computations\n";
        echo $title . " spent " . rutime($ru, $rustart, "stime") .
            " ms in system calls\n";
}

$test = array();
for($i = 0; $i<100000; $i++){
        $test[$i] = $i;
}

$rustart = getrusage();
for ($i = 0; $i<1000; $i++){
        array_splice($test,90000,1);
}
$ru = getrusage();
time_output('ArraySplice', $rustart, $ru);

unset($test);
$test = array();
for($i = 0; $i<100000; $i++){
        $test[$i] = $i;
}

$rustart = getrusage();
for ($i = 0; $i<1000; $i++){
        unset($test[90000]);
        $test = array_values($test);
}
$ru = getrusage();
time_output('UnsetReorder', $rustart, $ru);

回答4:

If you only remove the first item of the array, you could use array_shift($c);

回答5:

array_shift() shifts the first value of the array off and returns it, shortening the array by one element and moving everything down. All numerical array keys will be modified to start counting from zero while literal keys won't be touched.

array_shift($stack);

example:

$stack = array("orange", "banana", "apple", "raspberry");
$fruit = array_shift($stack);
print_r($stack);

Output:

Array
(
    [0] => banana
    [1] => apple
    [2] => raspberry
)

Source: http://php.net/manual/en/function.array-shift.php

回答6:

Or reset(); is also a good choice