从位置替换字符串中的数组

Question

I get trouble on replacing the word into special characters

First, I read the txt file and store each line into $line and put the special character that I want to change into $table array.

How do I change $line with special character $table array one by one based on the position for example, the txt include three words:

pads
password 
qwerty

so the program should show

p@ds
p@d$
p@ssword
p@$sword
p@$$word
p@$$w0rd
qwerty

Now my work just change all special characters into a new word. but how to change it using foreach / for loop one by one based on the position My code as follows

 <?php

    $file = fopen("text.txt", "r"); 
    while(!feof($file)) {
    $line = fgets($file);  
    $line = rtrim ($line);    

    $table = array(
        'a'=>'@', 'o'=>'0', 's'=>'$',   
    );


    $length = strlen($line);
    for ($i=0 ; $i<$length ; $i++){ 
        $line = strtr ($line, $table);
        echo $line."<br>";
    };
    }
    fclose($file);
?>

Answer 1

This should do the job (haven't tested it):

$char_array = str_split($line);
$replaced = FALSE;
foreach($char_array as $char) {
    if(array_key_exists($char, $table)) {
        $line = str_replace($char, $table[$char], $line, 1);
        echo $line."<br>";
        $replaced = TRUE;
    }
}
if(!$replaced)
    echo $line."<br>";

By setting the count argument of str_replace to 1, you make sure only the current character is replaced and not all of them.