substr_replace seems to fail

[davidannis]

I am playing with genetics and language, and can't get substr_replace to work. In the code fragment below I expect a mutation to change a character to another random character at random intervals. I put in a die to kill the process after the first replacement.

print_r($individuals);
foreach ($individuals as $key => $genome) {
            for ($x=0; $x<$num_offspring; $x++){
                $progeny[($key*$x)+$x]=$individuals[$key];
                for ($letter=0; $letter<strlen($progeny[$key*$x+$x]); $letter++){
                    //
                    if ((mt_rand(1,100))<=$mutation_rate){
                        //echo $x;
                        //print_r ($chars);
                        $replacement = $chars[mt_rand(0, (count($chars)-1))];
                        echo "<p>replacement: $replacement letter $letter x $x progeny # ";
                        echo $key*$x+$x."</p>\n";

                        echo "substr_replace(".$progeny[$key*$x+$x].",$replacement, $letter, 1)";
                        substr_replace($progeny[$key*$x+$x],$replacement, $letter, 1);
                        die($progeny[$key*$x+$x]);
                    }
                            
                }
}
        }

and I get output like this:

cTRcXiAirWYhWJTXp.gMFsHkUIqmle.WEJEe.Umx
Array ( [0] => cTRcXiAirWYhWJTXp.gMFsHkUIqmle.WEJEe.Umx )

replacement: e letter 0 x 0 progeny # 0
substr_replace(cTRcXiAirWYhWJTXp.gMFsHkUIqmle.WEJEe.Umx,e, 0, 1)cTRcXiAirWYhWJTXp.gMFsHkUIqmle.WEJEe.Umx

I expect that the first letter would change from a c to an e but it doesn't. I must be using substr_replace wrong, but I can't see where. What am I missing?

[akphidelt2007]

substr_replace does not change the array. You have to store it in a variable or include it in the die statement

 

So when you say die($progeny[$key*$x+$x]);... it is still going to contain the same value that it was before substr_replace.

 

Do...

$replace = substr_replace($progeny[$key*$x+$x],$replacement, $letter, 1);
die($replace);

[davidannis]

I can't believe I did that. Thanks for the help.