How can I find, increment and replace in php?
I have strings in the form \d+_开发者_如何学C\d+
and I want to add 1 to the second number. Since my explanation is so very clear, let me give you a few examples:
- 1234567_2 should become 1234567_3
- 1234_10 should become 1234_11
Here is my first attempt:
$new = preg_replace("/(\d+)_(\d+)/", "$1_".((int)$2)+1, $old);
This results in a syntax error:
Parse error: syntax error, unexpected T_LNUMBER, expecting T_VARIABLE or '$' in [...] on line 201
Here is my second attempt
$new = preg_replace("/(\d+)_(\d+)/", "$1_".("$2"+1), $old);
This transforms $old = 1234567_2 into $new = 1234567_1, which is not the desired effect
My third attempt
$new = preg_replace("/(\d+)_(\d+)/", "$1_".((int)"$2"+1), $old);
This yeilds the same result.
By making these attempts, I realized I didn't understand how the new $1, $2, $3, .. variables really worked, and so I don't really know what else to try because it seems that these variables no longer exist upon exiting the preg_replace function...
Any ideas?
$new = preg_replace("/(\d+)_(\d+)/e", '"$1_" . ("$2" + 1)', $old);
The $1
etc terms are not actually variables, they are strings that preg_replace
will interpret in the replacement text. So there is no way to do this using straight text-based preg_replace
.
However, the /e
modifier on the regular expression asks preg_replace
to interpret the substitution as code, where the tokens $1
etc will actually be treated as variables. You supply the code as a string, and preg_replace
will eval()
it in the proper context, using its result as the replacement.
Here's the solution for the PHP 5.3 (now when PHP supports lambdas)
$new = preg_replace_callback("/(\d+_)(\d+)", function($matches)
{
return $matches[1] . (1 + $matches[2]);
}
, $new);
Use explode
(step-by-step):
$string = "123456_2";
echo $string;
$parts = explode("_", $string);
$lastpart = (int)$parts[1];
$lastpart++;
$newstring = $parts[0] . "_" . (string)$lastpart;
echo $newstring;
This separates the string on the "_" character and converts the second part to an integer. After incrementing the integer, the string is recreated.
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