Using str_replace so that it only acts on the first match?

Question

I want a version of str_replace() that only replaces the first occurrence of $search in the $subject. Is there an easy solution to thi

Answer 1

$str = "/property/details&id=202&test=123#tab-6p";
$position = strpos($str,"&");
echo substr_replace($str,"?",$position,1);

Using substr_replace we can replace the occurrence of first character only in string. as & is repeated multiple times but only at first position we have to replace & with ?

Answer 2

I wondered which one was the fastest, so I tested them all.

Below you will find:

• A comprehensive list of all the functions that have been contributed onto this page
• Benchmark testing for each contrubution (average execution time over 10,000 runs)
• Links to each answer (for the full code)

---

All functions were tested with the same settings:

$string = 'OOO.OOO.OOO.S';
$search = 'OOO'; 
$replace = 'B';

---

Functions that only replace the first occurrence of a string within a string:

• substr_replace($string, $replace, 0, strlen($search));

  [CONTRIBUTED BY] => zombat
  [OOO.OOO.OOO.S] => B.OOO.OOO.S
  [AVERAGE TIME] => 0.0000062883
  [SLOWER BY] => FASTEST
  

• replace_first($search, $replace, $string);

  [CONTRIBUTED BY] => too much php
  [OOO.OOO.OOO.S] => B.OOO.OOO.S
  [AVERAGE TIME] => 0.0000073902
  [SLOWER BY] => 17.52%
  

• preg_replace($search, $replace, $string, 1);

  [CONTRIBUTED BY] => karim79
  [OOO.OOO.OOO.S] => B.OOO.OOO.S
  [AVERAGE TIME] => 0.0000077519
  [SLOWER BY] => 23.27%
  

• str_replace_once($search, $replace, $string);

  [CONTRIBUTED BY] => happyhardik
  [OOO.OOO.OOO.S] => B.OOO.OOO.S
  [AVERAGE TIME] => 0.0000082286
  [SLOWER BY] => 30.86%
  

• str_replace_limit($search, $replace, $string, $count, 1);

  [CONTRIBUTED BY] => bfrohs - expanded renocor
  [OOO.OOO.OOO.S] => B.OOO.OOO.S
  [AVERAGE TIME] => 0.0000083342
  [SLOWER BY] => 32.54%
  

• str_replace_limit($search, $replace, $string, 1);

  [CONTRIBUTED BY] => renocor
  [OOO.OOO.OOO.S] => B.OOO.OOO.S
  [AVERAGE TIME] => 0.0000093116
  [SLOWER BY] => 48.08%
  

• str_replace_limit($string, $search, $replace, 1, 0);

  [CONTRIBUTED BY] => jayoaK
  [OOO.OOO.OOO.S] => B.OOO.OOO.S
  [AVERAGE TIME] => 0.0000093862
  [SLOWER BY] => 49.26%
  

---

Functions that only replace the last occurrence of a string within a string:

• substr_replace($string, $replace, strrpos($string, $search), strlen($search));

  [CONTRIBUTED BY] => oLinkSoftware - modified zombat
  [OOO.OOO.OOO.S] => OOO.OOO.B.S
  [AVERAGE TIME] => 0.0000068083
  [SLOWER BY] => FASTEST
  

• strrev(implode(strrev($replace), explode(strrev($search), strrev($string), 2)));

  [CONTRIBUTED BY] => oLinkSoftware
  [OOO.OOO.OOO.S] => OOO.OOO.B.S
  [AVERAGE TIME] => 0.0000084460
  [SLOWER BY] => 24.05%
  

Answer 3

Unfortunately, I don't know of any PHP function which can do this.
You can roll your own fairly easily like this:

function replace_first($find, $replace, $subject) {
    // stolen from the comments at PHP.net/str_replace
    // Splits $subject into an array of 2 items by $find,
    // and then joins the array with $replace
    return implode($replace, explode($find, $subject, 2));
}

Answer 4

To expand on zombat's answer (which I believe to be the best answer), I created a recursive version of his function that takes in a $limit parameter to specify how many occurrences you want to replace.

function str_replace_limit($haystack, $needle, $replace, $limit, $start_pos = 0) {
    if ($limit <= 0) {
        return $haystack;
    } else {
        $pos = strpos($haystack,$needle,$start_pos);
        if ($pos !== false) {
            $newstring = substr_replace($haystack, $replace, $pos, strlen($needle));
            return str_replace_limit($newstring, $needle, $replace, $limit-1, $pos+strlen($replace));
        } else {
            return $haystack;
        }
    }
}

Answer 5

You can use this:

function str_replace_once($str_pattern, $str_replacement, $string){ 

        if (strpos($string, $str_pattern) !== false){ 
            $occurrence = strpos($string, $str_pattern); 
            return substr_replace($string, $str_replacement, strpos($string, $str_pattern), strlen($str_pattern)); 
        } 

        return $string; 
    } 

Found this example from php.net

Usage:

$string = "Thiz iz an examplz";
var_dump(str_replace_once('z','Z', $string)); 

Output:

ThiZ iz an examplz

This may reduce the performance a little bit, but the easiest solution.

Answer 6

If you string does not contains any multibyte characters and if you want to replace only one char you can simply use strpos

Here a function who handle errors

/**
 * Replace the first occurence of given string
 *
 * @param  string $search  a char to search in `$subject`
 * @param  string $replace a char to replace in `$subject`
 * @param  string $subject
 * @return string
 *
 * @throws InvalidArgumentException if `$search` or `$replace` are invalid or if `$subject` is a multibytes string
 */
function str_replace_first(string $search , string $replace , string $subject) : string {
    // check params
    if(strlen($replace) != 1 || strlen($search) != 1) {
        throw new InvalidArgumentException('$search & $replace must be char');
    }elseif(mb_strlen($subject) != strlen($subject)){
        throw new InvalidArgumentException('$subject is an multibytes string');
    }
    // search 
    $pos = strpos($subject, $search);
    if($pos === false) {
        // not found
        return $subject;
    }

    // replace
    $subject[$replace] = $subject;

    return $subject;
}