PHP 8 reference · String Functions

PHP substr_replace() Function

Replace part of a string, given a start position and length, with another string. Also inserts text or masks digits.

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Syntax

substr_replace(array|string $string, array|string $replace, array|int $offset, array|int|null $length = null): string|array

Parameter	Description
`string`	The input string.
`replace`	The text to put in.
`offset`	Where to start; negative counts from the end.
`length` optional	How many bytes to replace. `0` inserts without removing; `null` replaces to the end.

The new string.

Mask a card numberTry it yourself

<?php
$card = "4111222233334444";
echo substr_replace($card, str_repeat("*", 12), 0, 12), "\n";

Output

************4444

Insert and replace the endTry it yourself

<?php
echo substr_replace("Hello World", "Big ", 6, 0), "\n";  // insert
echo substr_replace("report.txt", "pdf", -3), "\n";      // replace the end

Output

Hello Big World
report.pdf

Version	Change
PHP 4.0	Added

str_replace() · Replace every occurrence of a search string with a replacement. Accepts arrays to make several replacements at once.
substr() · Return part of a string, given a start position and an optional length. Negative values count from the end.
PHP Strings · tutorial