Something wrong with array

Question

I'm using this code to get first number and replace it with 0-9, but I always get 0-0-9 result. Then I deleted in array 9 it started to work correct. why it works that way ?

$direction = strtoupper(substr($query_row["Band"],0,1));

$replace = [
'0' => '0-9','1' => '0-9','2' => '0-9','3' => '0-9','4' => '0-9',
'5' => '0-9','6' => '0-9','7' => '0-9','8' => '0-9', '9' => '0-9' ];

$dir= str_replace(array_keys($replace), $replace, $direction);

i understood your problem why it is happening as you replace 0 => 0-9 and then 9 => 0-9 which means 0 becomec 0-0-9 Searching for a solution please wait — Cybersupernova
– Cybersupernova, Commented Oct 30, 2015 at 10:20
I think you have a problem with multiple numbers in $direction. If you have more than 1 number it will replace all of these, not only the first one. Please give an example for $direction and an expected result. — tino.codes
– tino.codes, Commented Oct 30, 2015 at 10:21
Post the value of $direction too. Along with expected output — Narendrasingh Sisodia
– Narendrasingh Sisodia, Commented Oct 30, 2015 at 10:24

Cybersupernova · Accepted Answer · 2015-10-30 10:29:36Z

1

try this one

$search = array('0','1','2','3','4','5','6','7','8');
$replace = array('0-9','0-9','0-9','0-9','0-9','0-9','0-9','0-9','0-9');
$dir = str_replace($search, $replace, $direction);

and then work around for 9 which depends on your string mine was 0123456789 so I tried $dir = str_replace('99', '9,0-9', $dir);

its working on mine

answered Oct 30, 2015 at 10:29

Cybersupernova

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1 Comment

Joana Rudzis Over a year ago

Thank you, you set me on the way to fing out the solution. I changed fist $dir to $direct $dir = str_replace('99', '9,0-9', $dir); to $dir = str_replace('0-9-9', '0-9', $direct); :)

Community · Accepted Answer · 2020-06-20 09:12:55Z

It's explained in the documentation of str_replace():

Caution

Replacement order gotcha

Because str_replace() replaces left to right, it might replace a previously inserted value when doing multiple replacements.

You pass arrays as first two arguments to str_replace(). This is the same as you would call str_replace() repeatedly for each element in the array.

If $direction is not '9' then it replaces it with '0-9'. Then, on the last cycle it replaces '9' from '0-9' with '0-9' (according to the values you passed it).

I would drop the code after the first line and read the first sentence again: "get first number and replace it with 0-9".

If your goal is to get the first character of $query_row["Band"] and replace it with 0-9 if it is a digit (and make it uppercase otherwise) I would write something more simple:

$direction = substr($query_row["Band"], 0, 1);

if (is_numeric($direction)) {
    $dir = '0-9';
} else {
    $dir = strtoupper($direction);
}

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