PHP str_replace numbers with other numbers

Question

My string of numbers are not replacing correctly.

I am expecting the output after replacing to be 9876543210 but it doesnt seem to be the case.

What am i doing wrong?

<?php $numbers = array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9'); $code = array('9', '8', '7', '6', '5', '4', '3', '2', '1', '0'); $pre = '0123456789'; echo $pre . " ==> " . str_replace($numbers, $code, $pre); ?>

@HamZa : that's just a simple example I am thinking of jumbling the code in another order. @STTLCU : my output is 0123443210 — chongzixin
– chongzixin, Commented Jul 10, 2013 at 9:29
The problem is in the fact that the replace goes in the array order, that meaning that from 0 to 4 (at the beginning), the chars are replaced twice. Take a look at this example @ php.net php.net/manual/en/function.str-replace.php#example-4820 — Sebastian Neira
– Sebastian Neira, Commented Jul 10, 2013 at 9:31

Paul Dixon · Accepted Answer · 2013-07-10 09:28:45Z

That produces the output 0123443210 because str_replace with an array will start replacing earlier matches as it iterates over $numbers

For a single letter transposition like this, use strtr instead

 $encoded = strtr($pre, "0123456789", "9876543210");

Seems like a good looking replace. I think in this case this would be the more sensitive way of doing it.

HamZa · Accepted Answer · 2013-07-10 09:35:45Z

It's a bit long to explain but let me show you what's happening. For each element in the array it's replacing everything from the start from the string. Let's define N for $number and C for $code and R for $result

N C R 0 9 9123456789 1 8 9823456789 2 7 9873456789 3 6 9876456789 4 5 9876556789 5 4 9876446789 6 3 9873443789 7 2 9823443289 8 1 9123443219 9 0 0123443210

Thus you should use the solution provided by Paul using strtr()

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