regex preg_match for digit in middle for a string

问题

ddw_0_op1
ddw_1_op1
ddw_2_op1
ddw_3_op1
ddw_4_op1

in these strings of array how i can extract or preg_match only the number in middle that increase . thanks in advance

回答1:

I would break the string on underscore:

$parts = explode('_', $string);
$middle = $parts[1];

回答2:

If the number never exceeds a single digit, you could simply use $str[4] to get the fifth character of the string (your digit). On the other hand, however, if the numbers continue indefinitely, you could use either of the following regular expressions.

Option 1

See regex in use here

(?<=_)\d+(?=_)

(?<=_) Positive lookbehind asserting what precedes is _
\d+ Matches one or more digits
(?=_) Positive lookahead asserting what follows is _

Option 2

See regex in use here: This method uses fewer steps than the previous.

_\K\d+(?=_)

_ Match this literally
\K Resets the starting point of the reported match. Any previously consumed characters are no longer included in the final match
\d+ Matches one or more digits
(?=_) Positive lookahead asserting what follows is _

回答3:

use the preg_match function:

$str = "ddw_01_fdfd";
preg_match('/.+_([0-9]+)_.+/', $str, $matches);
echo $matches[1];

Output:

Another way to do it is by explode the string by _:

$xpl = explode('_', $str);
$middleStr = $xpl[1];

The explode function splits a string by string, in that case create an array made by all substring contained in $str dividing them by _.

Try it here.

来源：https://stackoverflow.com/questions/48627563/regex-preg-match-for-digit-in-middle-for-a-string

标签

php

regex

preg-match