I need to replace every occurrence of one of the letters a,o,i,e,u with [aoieu]?
I tried to do the following:
str_replace(array('a', 'o', 'i', 'e', 'u'), '[aoieu]?', $input);
But when giving it input of black instead of giving me the expected bl[aoieu]?ck it gave me
bl[a[ao[aoi[aoie[aoieu]?]?[aoieu]?]?[aoie[aoieu]?]?[aoieu]?]?[aoi[aoie[aoieu]?]?[aoieu]?]?[aoie[aoieu]?]?[aoieu]?]?ck
How can I get it to not replace things it already replaced?
You can consider using a regular expression for this, or you can make your own function which steps through the string one letter at a time. Here's a regex solution:
preg_replace('/[aoieu]/', '[aoieu]?', $input);
Or your own function (note that $search only can be a single char or an array of chars, not strings - you can use strpos or similar to build one which handles longer strings as well):
function safe_replace($search, $replace, $subject) {
if(!is_array($search)) {
$search = array($search);
}
$result = '';
$len = strlen($subject);
for($i = 0; $i < $len; $i++) {
$c = $subject[$i];
if(in_array($c, $search)) {
$c = $replace;
}
$result .= $c;
}
return $result;
}
//Used like this:
safe_replace(array('a', 'o', 'i', 'e', 'u'), '[aoieu]?', 'black');
I recommend avoiding preglike functions and using strtr().
This native function
Code:
$result = strtr($input, array('a' => '[aoieu]?',
'o' => '[aoieu]?',
'i' => '[aoieu]?',
'e' => '[aoieu]?',
'u' => '[aoieu]?'));
You might want to try this
<?php
$string = 'black';
$pattern = '/([aeiou])/i';
$replacement = '[aeiou]';
echo preg_replace($pattern, $replacement, $string);
?>
Replacement order gotcha
Because str_replace() replaces left to right, it might replace a previously inserted value when doing multiple replacements.
$input = str_replace(array('a', 'o', 'i', 'e', 'u'), '~', $input);
$input = str_replace('~', '[aoieu]?', $input);
~ in the input. Trivial reason that this is not a robust solution.
¯ or œ might do the trick.
Here it is:
$output = preg_replace('/[aeiou]/', '[aeiou]?', $input);
You might be able to get preg_replace to handle this for you (see Thax, Emil, etc.'s answers). Otherwise, if that is too complicated, you can, tokenize:
$token = '{{{}}}';
// replace the temporary value with the final value
str_replace( $token, '[aoieu]?',
// replace all occurances of the string with a temporary value.
str_replace( (array('a', 'o', 'i', 'e', 'u'), $token, $input ) );
