preg_split unexpected behavior

问题

I use preg_split as the following:

<?php
$num = 99.14;
$pat = "[^a-zA-Z0-9]";
$segments = preg_split($pat, $num);
print_r($segments);

I expected that $segments will be an array like array(99,14) However, it returns array(99.14) I don't know why preg_split do that while the pattern by which it should split the string is any special character i.e non alphanumeric.

Check this demo: http://codepad.org/MUusnwis

回答1:

You have to add delimiters to your regex like this:

<?php

    $num = 99.14;
    $pat = "/[^a-zA-Z0-9]/";
          //^------------^Delmimiter here
    $segments = preg_split($pat, $num);
    print_r($segments);

?>

Output:

Array ( [0] => 99 [1] => 14 )

EDIT:

The question why OP got the entire string back in the array is simple! If you read the manual here: http://php.net/manual/en/function.preg-split.php

And take a quick quote from there under notes:

Tip If matching fails, an array with a single element containing the input string will be returned.

回答2:

If you only want to split along the decimal, you could also use:

$array = explode('.', $num);

回答3:

You can also use T-Regx tool and you won't have such problems :)

Delimiters are not required

<?php
$num = 99.14;
$pat = "[^a-zA-Z0-9]";  // no delimiters :)
$segments = pattern($pat)->split($num);
print_r($segments);

来源：https://stackoverflow.com/questions/27808966/preg-split-unexpected-behavior