In this PHP tutorial, you shall learn how to insert a substring at specific index in the string using substr_replace() function, with example programs.
PHP – Insert character at specific index in string
To insert a substring at specific index in a string in PHP, call substr_replace()
function and pass the given string, the substring, index/position at which we need to insert the substring, and 0 as arguments.
Syntax
The syntax to insert a substring sub
in a string str
at index/position pos
is
substr_replace($str, $sub, $pos, 0)
Examples
1. Insert substring ‘abc’ in string at position 2
In this example, we take a string in str
, substring in sub
, position/index in pos
. We shall create a new string with the substring sub
inserted in the string str
at index pos
.
PHP Program
<?php $str = 'apple'; $sub = 'abc'; $pos = 2; $output = substr_replace($str, $sub, $pos, 0); echo 'Input : ' . $str . '<br>'; echo 'Output : ' . $output; ?>
Output

Conclusion
In this PHP Tutorial, we learned how to insert a given substring in a string at specific index/position, using substr_replace()
function, with the help of examples.