向 PHP 数组的每个项添加前缀

我有一个数字的 PHP 数组，我想用一个减号(-)作为前缀。我认为通过使用爆炸和内爆将是可能的，但我的 PHP 知识是不可能实际做到这一点。如果你能帮忙，我将不胜感激。

基本上，我想从这里开始:

$array = [1, 2, 3, 4, 5];

回到这里:

$array = [-1, -2, -3, -4, -5];

有什么想法吗？

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最佳答案

Simple:

foreach ($array as &$value) {
$value *= (-1);
}
unset($value);

Unless the array is a string:

foreach ($array as &$value) {
$value = '-' . $value;
}
unset($value);
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Something like this would do:

array_map(function($val) { return -$val;} , $array)
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In this case, Rohit's answer is probably the best, but the PHP array functions can be very useful in more complex situations.

You can use array_walk() to perform a function on each element of an array altering the existing array. array_map() does almost the same thing, but it returns a new array instead of modifying the existing one, since it looks like you want to keep using the same array, you should use array_walk().

To work directly on the elements of the array with array_walk(), pass the items of the array by reference ( function(&$item) ).

Since php 5.3 you can use anonymous function in array_walk:

// PHP 5.3 and beyond!
array_walk($array, function(&$item) { $item *= -1; }); // or $item = '-'.$item;

Working example

If php 5.3 is a little too fancy pants for you, just use createfunction():

// If you don't have PHP 5.3
array_walk($array,create_function('&$it','$it *= -1;')); //or $it = '-'.$it;

Working example

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An elegant way to prefix array values (PHP 5.3+):

$prefixed_array = preg_filter('/^/', 'prefix_', $array);

Additionally, this is more than three times faster than a foreach.

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$array = [1, 2, 3, 4, 5];
$array=explode(",", ("-".implode(",-", $array)));
//now the $array is your required array
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I had the same situation before.

Adding a prefix to each array value

function addPrefixToArray(array $array, string $prefix)
{
return array_map(function ($arrayValues) use ($prefix) {
return $prefix . $arrayValues;
}, $array);
}

Adding a suffix to each array value

function addSuffixToArray(array $array, string $suffix)
{
return array_map(function ($arrayValues) use ($suffix) {
return $arrayValues . $suffix;
}, $array);
}

Now the testing part:

$array = [1, 2, 3, 4, 5];

print_r(addPrefixToArray($array, 'prefix'));

Result

Array ([0] => prefix1 [1] => prefix2 [2] => prefix3 [3] => prefix4 [4] => prefix5)

print_r(addSuffixToArray($array, 'suffix'));

Result

Array ([0] => 1suffix [1] => 2suffix [2] => 3suffix [3] => 4suffix [4] => 5suffix)
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You can replace "nothing" with a string. So to prefix an array of strings (not numbers as originally posted):

$prefixed_array = substr_replace($array, 'your prefix here', 0, 0);

That means, for each element of $array, take the (zero-length) string at offset 0, length 0 and replace it the prefix.

Reference: substr_replace


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