Insert a character into a string at any position with PHP

To insert a character into another string using PHP, you need to use the substr_replace() function.

The substr_replace() function is used to replace a portion of a string.

The function accepts 4 arguments as shown below:

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

To insert characters without replacing the original string, you need to pass 0 as the $length argument of this function.

Let’s see an example. Suppose you need to insert the word very into the string I am feeling lucky today.

Here’s how you do it using substr_replace():

<?php

$str = "I am feeling lucky today";

$new_str = substr_replace($str, "very ", 13, 0);

print $new_str; // I am feeling very lucky today

To insert characters into a string, you need to count the index where you want to insert the string. A string index starts from the left at 0.

The word very needs to be placed before the word lucky.

The index of l in lucky is 13, so that’s what you need to pass as the $offset argument.

You also need to pass 0 as the $length argument, because the function will remove the rest of the string if you don’t pass any $length value:

<?php

$str = "I am feeling lucky today";

$new_str = substr_replace($str, "very ", 13);

print $new_str; // I am feeling very 

You can pass a single character or a string as the $replace() argument to the substr_replace() function.

Make sure that you pass the right $offset argument, or you will have a wrong string.

Now you’ve learned how to insert characters into a string at any position with PHP. Great job!