How Can I Replace Only the First Occurrence of a String in PHP?

Replacing Single Occurrences in Strings with Modified str_replace()

The built-in str_replace() function is a convenient tool for finding and replacing all occurrences of a specified string within a given subject string. However, there are situations where it is desirable to only replace the first occurrence of a string.

The Solution: Customizing Replace Behavior

While str_replace() does not have a built-in option to replace only the first match, a simple and efficient workaround can be implemented using the following steps:

1. Use strpos() to determine the position of the first occurrence of the search string within the subject string.
2. If a match is found, utilize substr_replace() to replace the portion of the subject string starting at the first match occurrence with the desired replacement string.

Here's an example code snippet:

$subject = "Hello world, world of programming!";
$search = "world";
$replace = "PHP";

$pos = strpos($subject, $search);
if ($pos !== false) {
    $newstring = substr_replace($subject, $replace, $pos, strlen($search));
}

echo $newstring; // Output: "Hello PHP, world of programming!"

This technique effectively replaces only the first occurrence of the search string, unlike str_replace(), which would replace all occurrences.

Additional Note

For scenarios where the last occurrence of a string needs to be replaced, the strrpos() function can be employed instead of strpos().

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