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

Replacing Only the First Occurrence with str_replace

There's no built-in variant of str_replace() that exclusively modifies a single occurrence. However, an elegant solution exists without resorting to convoluted approaches.

To limit replacement to the first match, employ the following procedure:

1. Utilize strpos() to locate the position of the initial $search occurrence within the $subject string.
2. If the position is not false, it means the occurrence was found.
3. Create a new string $newstring using substr_replace(). This function performs the replacement at the specified position for the duration of the $needle's length.

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

This method is highly efficient, sidestepping the potential performance hit associated with regular expressions.

Bonus:

For replacing the last occurrence, simply replace strpos() with strrpos() in the above code.

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