Support negative values

I’m in a situation where the CSV file is getting rid of the leading zero before my import and I need to be able to account for that. Let’s say that I have my value as the following:

-.0982739 -> I would want all case scenarios where it’s -. to turn into -0. – Here are my attempts:

if (str_contains($this->longitude, '-.')) {
    $this->longitude = '0' . $this->longitude;
};
Outputs: 00-.0989070

if ($this->longitude[0] == '.') {
    $this->longitude = '0' . $this->longitude;
}
Outputs: -.0989070

To simplify things, basically any . that has nothing before it, add in a 0, otherwise use the value given. I will need it for both longitude and latitude.

Answer

/^([-+])?./

The above regex matches the signs - and + if they are present and immediately followed by a .. Now, capture the matched group 1 in the regex which is ([-+])? and append 0. followed by all digits after . by taking substr of the current string.

<?php

$a = ".0982739";

if(preg_match('/^([-+])?./',$a, $matches) === 1){
    $prefix = $matches[1] ?? '';
    $a = $prefix . '0.' . substr($a,$prefix == '' ? 1 : 2);
}

echo $a;