How to implement replacement only once or N times in php, php replacement_PHP tutorial

How to achieve php replacement only once or N times, php replacement

We all know that in PHP, Strtr, strreplace and other functions can be used to replace, but they replace each time All are replaced, for example:
"abcabbc", if you use the function above to replace the b in this string, then it will replace all of them, but what if you want to replace only one or two? See the solution below:
This is a rather interesting question. I happened to have done similar processing before. At that time, I directly used preg_replace to implement it.

 mixed preg_replace ( mixed pattern, mixed replacement, mixed subject [, int limit] )
Searches the subject for a match of pattern and replaces it with replacement. If limit is specified, only limit matches are replaced; if limit is omitted or has a value of -1, all matches are replaced.
Because the fourth parameter of preg_replace can limit the number of replacements, it is very convenient to deal with this problem in this way. But after looking at the function comments about str_replace on php.net, we can actually pick out a few representative functions.

Method 1: str_replace_once
The ideaFirst find the location of the keyword to be replaced, and then use the substr_replace function to directly replace it.

<&#63;php
function str_replace_once($needle, $replace, $haystack) {
// Looks for the first occurence of $needle in $haystack
// and replaces it with $replace.
$pos = strpos($haystack, $needle);
if ($pos === false) {
// Nothing found
return $haystack;
}
return substr_replace($haystack, $replace, $pos, strlen($needle));
}
&#63;>

Method 2, str_replace_limit
The ideaStill uses preg_replace, but its parameters are more like preg_replace, and some special characters are escaped, making it more versatile.

<&#63;
function str_replace_limit($search, $replace, $subject, $limit=-1) {
// constructing mask(s)...
if (is_array($search)) {
foreach ($search as $k=>$v) {
$search[$k] = '`' . preg_quote($search[$k],'`') . '`';
}
}
else {
$search = '`' . preg_quote($search,'`') . '`';
}
// replacement
return preg_replace($search, $replace, $subject, $limit);
}
&#63;>

You can study together with an article compiled by the editor before, "Implementation Function of PHP Keyword Replacement Only Once". I believe you will have unexpected gains.

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