Write a PHP script to Replace the first word with another word

 Write a PHP script to replace the first 'what' of the following string with 'how'

preg_replace():-

The preg_replace() function returns a string or array of strings where all matches of a pattern or list of patterns found in the input are replaced with substrings.

There are three different ways to use this function:

1. One pattern and a replacement string. Matches of the pattern are replaced with the replacement string.

2. An array of patterns and a replacement string. Matches any of the patterns are replaced with the replacement string.

3. An array of patterns and an array of replacement strings. Matches of each pattern are replaced with the replacement string at the same position in the replacements array. If no item is found at that position the match is replaced with an empty string.

Replacement strings may contain a backreference in the form \n or $n where n is the index of a group in the pattern. In the returned string, instances of \n and $n will be replaced with the substring that was matched by the group or, if \0 or $0 are used, by the whole expression.

synatx:-

preg_replace(patterns, replacements, input, limit, count)

code:-

<?php

$str = 'hello friends what are you';

echo preg_replace('/what/', 'how', $str, 1); 

?>

output:-

hello friends how are you