I have a PHP array of numbers, which I would like to prefix with a minus (-). I think through the use of explode and implode it would be possible but my knowledge of php is not possible to actually do it. Any help would be appreciated.
Essentially I would like to go from this:
$array = [1, 2, 3, 4, 5];
to this:
$array = [-1, -2, -3, -4, -5];
Any ideas?
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.
preg_replace, it does roughly the same but it always returns a same-sized array with the unmodified item for items that doesn't match the regex. It's also a bit lighter on the version requirements (exists in PHP4 vs preg_filter which requires PHP >= 5.3.0).
$ anchor: preg_filter('/$/', '_suffix', $array);preg_filter('/^(.*?)$/', '$0*', $array), it does work, but i like yours, it is short. thanks again really appreciate the help :)
preg_replace by the way.Simple:
foreach ($array as &$value) {
$value *= (-1);
}
unset($value);
Unless the array is a string:
foreach ($array as &$value) {
$value = '-' . $value;
}
unset($value);
foreach ($array as &$value){ /* ... */ } unset($value);.
In this case, Rohit's answer is probably the best, but the PHP array functions can be very useful in more complex situations.
You can use array_walk() to perform a function on each element of an array altering the existing array. array_map() does almost the same thing, but it returns a new array instead of modifying the existing one, since it looks like you want to keep using the same array, you should use array_walk().
To work directly on the elements of the array with array_walk(), pass the items of the array by reference ( function(&$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;
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;
Something like this would do:
array_map(function($val) { return -$val;} , $array)
print_r($array) would show $array unchanged after the above. - If you assign the returned value to $array this'll get the job done nicely.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
$array = [1, 2, 3, 4, 5];
$array=explode(",", ("-".implode(",-", $array)));
//now the $array is your required array
, then the resulting array will have more items than the original. This does work for the OPs case where it is just numbers.I had the same situation before.
function addPrefixToArray(array $array, string $prefix)
{
return array_map(function ($arrayValues) use ($prefix) {
return $prefix . $arrayValues;
}, $array);
}
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'));
Array ([0] => prefix1 [1] => prefix2 [2] => prefix3 [3] => prefix4 [4] => prefix5)
print_r(addSuffixToArray($array, 'suffix'));
Array ([0] => 1suffix [1] => 2suffix [2] => 3suffix [3] => 4suffix [4] => 5suffix)
