PHP: convert string to float (only if string represents a float)

Question

I have an unknwon string that could resemble a float. In that case I want to convert it to float (for calculations), otherwise leave it as a string.

Answer 1

Because it hasn't been mentioned

if(preg_match('/^\d+\.\d+$/', $string)){
   $float = (float)$string;
}

I think is_numeric is a better choice, but this works too.

What I have above only matches floats, so they have to have the decimal. To make that optional use /^\d+(\.\d+)?$/ instead.

• ^ start of string
• \d+ one or more digits
• \. the dot, literally
• \d+ one or more digits
• $ end of string

For the second one /^\d+(\.\d+)?$/ it's the same as the above except with this addition:

• (...)? optional capture group, match this pastern 0 or 1 times.

Which it should now be obvious is what makes the decimal optional.

Cheers!